The Right Blue: diver tips

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Watching and being watched underwater

by B. N. Sullivan

Recreational divers are essentially underwater sightseers. Just like sightseers on land, they take in the scenery and observe 'the locals' going about their business. In this case, of course, the locals are the critters that inhabit the reef.

But make no mistake, this isn't a one-way activity. The critters watch us just as we watch them. We've mentioned this a few times in the past. Longtime readers of The Right Blue may recall the story of Brutus, the Great Barracuda, who seemed to be attracted to Jerry's black and yellow wetsuit. Brutus took to following Jerry around on the reef -- again and again and again!

At least we knew Brutus was there -- really, you couldn't miss him! But sometimes creatures in the sea watch or even stalk divers while the diver is oblivious to their presence. As an example, we once posted a photo of a sneaky shark approaching a diver from behind, while the diver -- engrossed in what he was photographing -- remained unaware of the shark. Based on our own experiences, we think scenarios like that happen very often.

It's amazing how marine animals can seem to appear out of nowhere! We remember many occasions when animals startled us by literally swimming right over our shoulders. The photo at right is one example of that. I was photographing something -- I don't even remember what -- when this Gray Angelfish suddenly swooped into view from behind me. I pressed the shutter button just in time to capture the fish, rather than whatever it was I intended to photograph!

Many animals in the sea are curious about divers. Whales, dolphins, sharks, large jacks, eagle rays and turtles all have, on occasion, altered their course to approach us closely to look us over. Some have paused to watch whatever it was we were doing.

Sometimes, the critters seem to be hoping we will facilitate their search for a meal. Dig in the sand, or turn over a rock, and you are likely to attract any number of 'inspectors' watching to see if you have unearthed something they would like to eat. Direct a beam of light onto a reef during a night dive, and you may draw the attention of nocturnal hunters.

Usually these kinds of encounters are amusing, although sometimes they can give the diver quite a start, especially at night. We recall several instances when our hearts momentarily skipped a beat during night dives when large creatures we weren't expecting to see suddenly appeared at very close range -- like the huge Manta ray that hovered so closely above us that we could have reached up and tickled its big white belly; like the Great Barracuda that zoomed over my shoulder to snatch the little fish I was about to photograph; like the 'wolf pack' of five Gray Reef Sharks that swept past our backs so closely that we felt the turbulence, which caused us to whirl around and train our lights on them just in time to count them as they sped away down the reef.

There are several factors at work here. For one thing, a diver's visual field is reduced underwater, compared to what it would be on dry land. Even in the clearest water, a diver cannot see ahead more than, say, 45 meters (about 150 ft.) at most, and more often, horizontal visibility underwater is considerably less. Things near the limits of that visibility range appear as shadowy lumps rather than as well-defined objects (or critters!).

Another impediment is the diver's mask. It's true that without the mask -- and the airspace between the glass plate and the diver's eyes -- everything would look like a blur. But at the same time, the skirt of the mask tends to block the diver's peripheral vision -- not just side to side, but also above and below.

Finally, we don't usually hear an animal approaching us underwater. There are no sounds of footsteps, and while the exhaust bubbles from open circuit SCUBA make noise, most marine animals make no discernible sounds as they move about.

What to do? When you are diving, we suggest that you periodically glance up, and down, and look over your shoulder to see who or what may be watching you.

Wreck diving: Beware of entanglement

by B. N. Sullivan

What: This photo of Jerry ascending from a wreck dive is a reminder that the potential for entanglement is one of the hazards of diving on natural wrecks. Wrecks that have been intentionally sunk as artificial reefs and diver playgrounds usually are prepared ahead of time to minimize hazards that could lead to diver entanglement or entrapment. Doorways and portholes are removed or welded open, and cables, lines, and other sources of entanglement are taken off the vessel. This is not the case with natural wrecks, i.e., vessels that have sunk as a result of an accident, or war. Proper training in wreck diving will educate the diver about how to recognize and cope with the risks entailed in diving on natural wrecks.

Where: I took this photo of Jerry at the site of the wreck of the Zenobia, a modern ship that sank in 1980 off the coast of Larnaca, Cyprus. The Zenobia was a huge vessel, more than 172 meters (560 feet) in length, with a beam of about 23 meters (75 feet). Click here to see a photo of the Zenobia, just before she sank.

We made a number of dives on the wreck of the Zenobia in the 1990s. In case you missed our series of articles about those dives (with photos), here they are:

Fire Coral Redux

Our readers ask us a lot of questions about diving, about locations we have visited, and about marine life. Fire Coral is among the topics asked about most frequently. People want to know where it is, what it looks like, and what to do if they are stung by Fire Coral.

Back in late 2007, we posted two articles about Fire Coral, along with some photos of examples of the kinds of Fire Corals most commonly encountered by divers and snorkelers in the Caribbean Sea and the Red Sea. Although those articles receive a lot of traffic from search engines, we decided to post the links to both for the benefit of our newer readers who might not have known about them.

Fire Coral: Look, but do not touch gives an overview of Fire Coral, and how its nematocysts work to sting whoever brushes up against them. The article includes a photo of Millepora alcicornis, a Caribbean species of Fire Coral, and a macro photo that shows the dactylozooids, the tiny hair-like structures that contain the Fire Coral's stinging nematocysts.

Fire coral: Another view displays a wide-angle image of Millepora dichotoma, the Fire Coral species encountered most frequently in the Red Sea.

For those of you who prefer to listen rather than read, here is a video about Fire Coral, produced and narrated by Don Stark of ScubaVisions.com.

If the video does not play or display properly above, click here to view it on YouTube.

Diving with a Partner: Pre-dive checks are essential for dive safety

by B. N. Sullivan

I don't think there is a diver training program anywhere in the world that does not teach -- and emphasize -- the importance of the 'buddy system' for sport divers. The idea is to dive with a partner so that you can watch out for each other, and help each other if a problem arises.

In order for the buddy system to work optimally, dive partners need to know some things about each other's abilities, skill level, and equipment prior to entering the water. This is easier to do if you have one or more partners with whom you dive regularly, but it should be kept in mind regardless of whom you are paired with for a dive.

Let's take the case of diving with someone you don't know well or have just met. Don't be shy about asking the diver about the extent of his or her dive experience: what kind of training they have had, how often they dive, and how recently they have been in the water.

Certifications alone do not tell the whole story. A diver with a basic certification who does 50 dives a year may be a much more capable diver than, say, a certified rescue diver who only gets into the water a few times a year. Skills get rusty, and both competence and confidence erode with lack of practice.

The point of asking your prospective dive partner about experience and skills is not just a case of idle curiosity. You need to know the amount of monitoring your partner may need, and conversely, to what extent you can rely on that person to help you if you have a problem. If it sounds like there is a significant disparity between you and the other diver, it is wise to begin with very easy 'G-rated' dives with the person in order to minimize the risks while you get a fix on their skill level and comfort in the water.

Now, about equipment -- yours and your partner's. While all training agencies teach that you should dive with a buddy, some (I'm sorry to say) do not stress what is known as the pre-dive buddy check. The purpose of the buddy check is to ensure that each dive partner has all the essential equipment, that it is in good working order, and that each diver knows how to work the other's equipment.

The buddy check, plain and simple, is, "You show me yours and I'll show you mine."

We all use the same items of equipment when we dive, but there is a lot of variation among brands and models in regard to design and placement of controls. During the buddy check each diver shows the partner the location of every piece of critical gear, and demonstrates how it operates.

The idea is that if something untoward happens underwater, neither diver has to waste precious time fumbling about, trying to figure out how a partner's gear works. If I am your dive partner, I will want to know the following things -- at minimum -- about your equipment, and then I will show you the same things about mine.

Show me that the valve on your cylinder is turned on, and show me the display on the instrument you are using to gauge the remaining gas in your cylinder. I want to know how much air you have at the outset of the dive.
Show me your primary regulator, and demonstrate how the purge valve works. Then show me your back-up second stage - where it is stowed, and how it is released from where it is stowed. Then tell me whether you plan to hand off your primary or back-up second stage to me in an emergency.
Demonstrate your buoyancy compensating device (BCD). Show me how to inflate it, and also point out all the dump valves so I will know where they are.
Are you wearing a weight belt or are your weights integrated with your BCD? Do you have any extra weights in your pocket or in any unconventional places?
Show me the location of all the releases on your gear and how to work them -- especially for your weight system and BCD. Are they snaps, buckles, Velcro, pull-cords? I need to know what I am looking for in an emergency.
Show me your computer or other instruments. I don't want to have to figure out where to look on an unfamiliar display for critical information during an emergency.

Many divers are shy about asking a new dive partner to perform a buddy check and cross-check. Don't ever be shy about this. Be the one to initiate the buddy check; your partner will then doubtless go along.

If you are fortunate enough to have one or more regular dive partners, you probably are familiar with their equipment and know how it operates. But don't be complacent! Always check each other's gear configuration before entering the water. Weights in place? Air turned on? Instruments operating and displaying what you expect them to display?

I once had an experience that taught me not to ignore these things just because I was diving with someone I knew well. A frequent dive companion and I entered the water without doing a buddy check. We had been chatting and laughing while gearing up, creating just enough distraction so that we skipped cross-checking each other's equipment.

We were nearing 40 meters (about 130 ft), the deepest point of a our planned dive route, when I heard my companion shriek, right through her regulator. When I looked her way, I could see that she was alarmed. She turned the face of her air-integrated dive computer toward me, excitedly jabbing her finger at it. The display was blank -- no lights, no numerals, no data, nada!

We had to abort the dive then, of course. We stayed very close together as we gradually ascended during the hurried five minute swim back to our exit point. We had no idea how much air she had left, for openers. In fact, while we were swimming, it occurred to me that I did not even know how much air she had at the outset of the dive, since we had not done the buddy check and cross-check.

Once back on shore, we discovered that the problem was a dead battery in her computer. She admitted that she hadn't paid much attention to her computer display before the dive, since she 'knew' she had a full tank of air. For my part, I had never checked her equipment before the dive. I was annoyed with her, but I was really angry at myself. I knew better than that.

Had we done a routine check and cross-check, one of us might have noticed the low battery indicator. In any case, I would have known how much air she had started out with and might not have been quite so anxious during the swim back to shore from the depths.

Luck had been on our side, but it could have been a disaster. I learned my lesson. That was the last time I began a dive without a buddy check and cross-check.

The British Sub-Aqua Club (BSAC) is one training agency that does a good job of teaching and emphasizing the buddy check and cross-check to divers. They teach a mnemonic device to help divers remember the essential elements of the buddy check: B-A-R.

B is for Buoyancy
A is for Air
R is for Releases

Regardless of which agency trained you, think about adopting BSAC's 'B-A-R' to help you remember the items that need to be checked and cross-checked before you enter the water.

Stingrays: Dangerous or Not?

by B. N. Sullivan

Our previous pictorial post about a dive site in the Cayman Islands called Stingray City generated a lot of interest, and quite a few questions about stingrays. We decided to tell our readers some more about these interesting marine animals.

Stingrays are found in warmer waters around the world. Stingrays are Elasmobranchs - a classification of fishes that include sharks and other kinds of rays, like Mantas and Eagle Rays. Elasmobranchs differ from other fishes in that their skeletons are made of cartilage rather than bone.

There are many species of stingray. The species pictured on this page, and in our photo essay about Stingray City, is the Southern Stingray (Dasyatis americana). It can be found in the warmer latitudes of the Western Atlantic, and throughout the Caribbean and the Gulf of Mexico. They are found most often in relatively shallow waters where there are sandy bottoms, because that is where they find their food.

The diet of these creatures consists of small animals that live in the sand - mostly shellfish, small crustaceans and worms. The stingray feeds by hovering directly over the sand and fluttering the wing-like edges of its body disc to clear away the top level of sand. This exposes the little creatures that live just under the sand, and the stingray plops on top of them and eats them.

The photos in an earlier post on The Right Blue shows a Southern Stingray hunting for its dinner on a sand flat in the Turks and Caicos Islands.

The stingray's mouth and gill slits are on the underside of the body. You can see the mouth and gill slits clearly in the second photo of our post about Stingray City. The stingray's eyes are on the top of its body, as you can see in the photos on this page. When stingrays lie on the sand, they flutter their 'wings' a bit to cover themselves with sand until only their eyes and the end of their tail are visible.

But what about the 'stinger' that gives the stingray its common name?

The 'stinger' actually is a barbed spine that is located at the base of the stingray's tail. The barb contains a venom and is the stingray's defensive weapon. It does not use the barb on prey.

Stingrays spend a lot of time swimming just over the surface of sandy bottoms, looking for food. When they feed, and sometimes when they rest, they settle onto the bottom and lie flat. Thus, whether resting or hunting, they are subject to predation from above. If they are disturbed from above while they are on the sand, they quickly erect the barbed spine at the base of their tail as a defense.

The stingray's tail does not have a 'stinger' at the end of it, and they do not sting divers or prey by whipping their tails around. Most people who have had nasty encounters with stingrays have been divers and waders who accidentally stepped on a ray, or swam closely over one that was half-buried in the sand.

Many people will recall that Steve Irwin, the well-known Australian environmentalist and television personality, met his death after an unfortunate encounter with a stingray in 2006. Ironically, Steve was filming an underwater documentary about the ocean's deadliest creatures at the time of the incident.

Apparently Steve Irwin either laid down on top of a stingray, or swam just a few inches above where one was buried in the sand. The stingray did what stingrays do when some creature threatens them from above: it quickly raised the barbed spine at the base of its tail. Unfortunately, the barb pierced Steve Irwin's chest.

Irwin's death was sobering to divers and especially to underwater photographers. I think it is safe to say that every underwater photographer or videographer in the world has spent a considerable amount of time lying or kneeling on the sand to take pictures. Steve Irwin's death was a dramatic reminder to look carefully at the surface of the sand for evidence of a partially buried stingray before settling there.

So, are stingrays dangerous? In certain circumstances, yes; in most cases, no.

Here are some earlier posts on The Right Blue that feature stories and photos of stingrays:

Stingray City, Grand Cayman Island - photos of a Southern Stingrays interacting with divers
Picture this! - photos of a Southern Stingray hunting with a Bar Jack (Caranx ruber)
The 'eyes' have it - features close-up images of a Blue-spotted Stingray (Taeniura lymma)
Blue Spotted Stingray at Pulau Sipadan - photo only
On a collision course with critters in the sea - story and photo of a large deep-dwelling stingray species in Hawaii (at the bottom of the page)

Diving Is Not for Everyone

by B. N. Sullivan

We are contacted rather frequently by readers who want to know if we are diving instructors. After reading The Right Blue, they say, they want to learn how to dive, and they would like to learn from us.

We are always touched and flattered by those kinds of messages, but we have to say that no, we are not dive instructors. Both of us are trained and certified as divemasters, but we don't work as divemasters or dive guides either. As we explained in a much earlier post, we became certified as divemasters out of self-interest -- so that we would be qualified to manage our own dives, both at home and when we travel.

Nevertheless, we have coached many new divers to help them develop their skills, and we have advised many others on issues pertaining to diver training, equipment choice, and the like. We are happy to share what we know -- we just do it in an informal manner.

Quite recently, we have had a flurry of inquiries from people who are just beginning their first diving course, or who are thinking of doing so in the near future. Several have expressed a combination of enthusiasm and reservation: They want to learn to dive, but at the same time, they are more than a bit scared.

We have responded individually to those inquiries, but we thought it might be a good idea to share publicly some of what we said, for the benefit of other prospective divers who were too shy to ask us directly. This will be the first in a series of articles about learning to dive.

If you love being in and around the water, you're in reasonably good physical shape, you love to swim and are comfortable in lakes or the sea, and you want to learn to dive, go for it! Seek out a reputable instruction program that offers a widely recognized certification, and dive right in.

But what if you're not such a good swimmer? What if most of your swimming has taken place in pools and you're worried about diving in open water? Should you sign up for a scuba course and hope for the best?

Every dive instructor can recount stories of people who showed up for their first dive class, barely able to doggie paddle across the width of a backyard pool. What were they thinking? One total non-swimmer who showed up for a class run by an instructor friend of ours said she figured it didn't matter that she didn't know how to swim on the surface. She believed that having an air supply would make up for the fact that she didn't even know how to float! The instructor gently pointed out that eventually she would at least need to swim to and from the beach or dive boat, so if she couldn't do that, she would not be able to proceed with the dive course.

If you are not a reasonably good swimmer, or if you are not confident of your skills in the water, it might be a good idea to work on improving your swimming skills before you begin diving instruction. You don't have to be a champion swimmer, you don't need to be able to swim fast, and you don't need to have perfect form, but you should have mastered basic competencies like being able to tread water for several minutes, swim several lengths of a pool un-aided, and so on.

If most of your swimming has been in pools, and rarely in natural bodies of water - lakes, rivers, sea -- then you may feel anxious when you first venture into open water. There's something about all that open space -- the lack of visible walls and a nice flat, clean pool bottom -- that unnerves some people the first time they go swimming in the ocean or a large lake.

Lots of pool swimmers have good basic skills, but they have to learn what to do about things like surface chop, swells, waves and currents. They often have initial fears about all those creatures in the open water, too. If you have been mostly a pool swimmer, we advise that you spend some time snorkeling in natural bodies of water before you begin scuba lessons, just to become more comfortable with the conditions and surroundings.

Some people sign up for scuba instruction solely because they are urged to do so by someone else. Their spouse or significant other (or parent, child, cousin, friend) either is a diver, or is learning to dive, and wants a companion. We would be the first to tell you that having a regular dive partner that you know well away from diving is a wonderful thing. But if you are going to take dive lessons only because someone else has urged you to do so, it may be a mistake -- especially if some of the factors above, relating to swimming skills and comfort in the water, also apply.

Lots of couples and pairs or groups of friends learn to dive together. Some become lifelong dive companions. However, if you are otherwise uninterested in diving, or you are uncomfortable in the water, but you are being nudged to go through a course to satisfy someone else, you might want to reconsider.

Again, the key factor is comfort. If you are not at ease while swimming in the ocean or a lake, if you are not confident of your swimming skills, diving may not be right for you at this time. Once you spend more time in the water, and once you improve your skills so that you feel relaxed, then you can think about learning to dive.

We hope the title of this article does not put off would-be divers. We like to promote sport diving for people who really want to do it, but some people are just not well suited to be divers. We think it's better to take a realistic look at your own suitability -- your skills and limitations -- ahead of time.

If your skills or comfort level in the water are less than optimal but you really want to dive, you can and should prepare to do it. If you are planning to learn to dive only because someone else wants you to do it, think again. Diving is not for everyone.

Conus striatus - A fish-eating cone shell

by B. N. Sullivan

In a recent post, we introduced our readers to Cone Shells, and the snails that make those shells and live in them. We mentioned that the Cone Shell snails have a venomous sting, making them potentially dangerous to handle when they are alive.

Unlike some other mollusks, which eat algae, the animals that inhabit Cone Shells are carnivorous , and they use their venom, which is a neurotoxin, to immobilize or kill their prey. Some Cone Shell snails eat other mollusks, while others eat marine worms. A few Cone Shell species, like the one on this page, actually eat fish!

This is the Striated Cone (Conus striatus), a relatively large Cone Shell species. The one pictured here is from our shell collection. We found it in a sandy patch at a depth of about 6 meters (20 ft) off the coast of Puako, Hawaii. It is 10.4 cm in length (about 4.25 in). The Striated Cone is uncommon -- that is, it is not abundant in most locations. At the same time, though, it is widely distributed. It can be found in many different locations around the Indo-Pacific region, from the Red Sea all the way to Hawaii.

The Striated Cone is one of the Cone Shell species considered to be potentially dangerous to humans. For one thing, its venom is among the most potent. For another, the snail is amazingly flexible and agile. Its siphon and proboscis (where the stinging radula teeth are located) can be extended nearly the length of its shell. Thus, even if you are careful to hold a live Striated Cone Shell by the widest end, it still may be possible for it to sting you.

The Striated Cone snail hunts primarily at night. A wily predator, its method is to sneak up on a small fish that is 'sleeping' on the bottom and sting it, injecting it with venom. The neurotoxic venom paralyzes the little fishy. Once the prey is thus immobilized, the snail literally engulfs it.

You might imagine that it would take quite awhile for a snail to engulf a fish. In fact, the snail's proboscis (mouth) expands and it hoovers in the prey in a remarkably short time, swallowing it whole.

Don't believe me? Have a look at this video of Striated Cone Shell snail attacking and consuming a little fish: .

If the video does not play or display properly above, click here to view it on YouTube.

NOTE: This post was included in the Carnival of the Blue 23 over at Deep Sea News. (Thanks, Kevin.) We invite all of our readers to drop by the Carnival for more wonderful articles about the sea and its fascinating inhabitants.

Collecting Cone Shells: Special Handling Required

by B. N. Sullivan

In the last several posts we have been talking about collecting sea shells, and how divers can find shells underwater.

We strongly discourage the taking of live shells from their habitat. Taking live shells depletes populations by preventing the creatures living inside from reproducing. It also can disrupt the ecological balance of the habitat, since these creatures have roles as both predators and prey.

Previously, we offered a few tips on how to figure out if there are creatures living inside a shell. Today we would like to add a word of caution, particularly in regard to Cone Shells (Conidae).

There are hundreds of species of Cone Shells. The shells are attractive, and popular with collectors, but you should know that the snails that build and inhabit Cone Shells are venomous. Handling a live Cone Shell can result in being stung.

The Cone Shell snails are carnivores: some prey on other mollusks, others eat worms, and still others actually prey on fish! The snails have a structure that works a bit like a hypodermic syringe. They produce a venom that contains neurotoxins. They inject the venom into their prey through hollow stingers. (Technically, the 'stingers' are tiny, harpoon-like radula teeth.) Depending on the species, the venom either kills or immobilizes the prey.

There have been numerous cases documenting Cone Shell envenomation in humans. Depending, again, on the Cone Shell species, and also on the site of the sting, the result can range from pain, to paralysis, to death! So, if you see a Cone Shell in the water, understand that it is a venomous creature, and approach it accordingly.

If you are going to handle a Cone Shell to see if it is alive, pick it up carefully by the crown -- that is, the broad end of the cone. The stinging part is in the proboscis, which is at the 'nose' of the cone. Better yet, use something inanimate as a tool to flip over the shell so that its aperture faces upward. You may immediately see some part of the snail, but even if you don't, you should wait for awhile to see if the animal appears and tries to right itself.

If you find shells -- including Cone Shells -- while diving, it's convenient to carry them in a small mesh bag that you can clip to a D-ring on the outside of your vest. In any event, do NOT put a cone shell into your pocket or carry it in your hand, even if you think it is empty -- just in case!

We recommend that divers (and others) who are interested in collecting shells learn something about the creatures that formed the shells and live inside them. An understanding of how and where they live, what they eat -- and what eats them -- not only facilitates knowing where to look for them, it also provides the collector with a better appreciation of how the creature fits into the ecosystem. Today we add another item to this list of reasons to learn something about these creatures: your own self-protection.

About the photos: I took these macro photos of a live Mediterranean Cone Shell (Conus mediterraneus) on a sand flat off the coast of Dhekelia, Cyprus. As far as I know, this is the only Cone Shell species native to the Mediterranean Sea. The shell is relatively small -- about 3 cm (1.25 in). By the way, despite its appearance, that brownish structure sticking out near the wide end of the shell in the second photo is not the 'stinger'. It is the snail's operculum - a sort of lid that the snail uses to close over the shell aperture for protection when it retracts into the shell. The operculum is hard, made of material similar to our fingernails.

Curiously, we have never found an empty Mediterranean Cone Shell, so we have no examples of this shell in our collection. Fortunately, we do have several nice photos of the living species. Some long-time readers of The Right Blue may recall another post featuring this species, from 2007: Muck diving - The tale of the cross-eyed cone shell

Air Sharing Pointers for Divers

by B. N. Sullivan

Basic diver certification courses all include instruction on air sharing. (For our non-diving readers, 'air-sharing' refers to more than one diver using the same air source.) This is a very basic and essential skill, and these days it is also quite easy, in principle.

Back in the day when I first learned to dive, SCUBA regulators only had one second stage, i.e., the part of the regulator that includes the mouthpiece. In order to share air, one diver had to take the regulator out of his/her mouth and hand it to the other diver. The second diver would take a breath or two, and then pass the regulator mouthpiece back to the first diver. This alternating pattern would continue until the divers could surface. The procedure worked, of course, but it could be quite awkward. Also, since neither diver could breathe continuously, both divers could end up experiencing considerable anxiety.

These days, most divers use regulators that have two second stages, each attached to its own low-pressure port on the regulator's first stage, i.e., the part that connects to the valve of the air cylinder. Look at the photo of our friend Dan on this page. You can see that his regulator has two second stages. The hose of the primary one passes over his right shoulder, and he is breathing through the mouthpiece. The hose of the secondary one passes under his arm, with the mouthpiece attached to his vest with a quick-release clip. This is a standard sport diving configuration.

In a popular alternative configuration, the inflator hose for the diver's buoyancy compensator has a mouthpiece on it so that it can double as a breathing device.

The advantage of using regulators with two second stages should be obvious: two divers can share the same air source simultaneously and continuously, without the need to pass the mouthpiece back and forth between them. This makes air sharing much easier, and is less anxiety-producing.

Divers are taught how to signal to each other that they need to share air, and the procedure of handing off the secondary regulator to the diver in need of air is practiced during training. They are taught that as soon as air sharing begins, the divers should begin their ascent together.

I take issue with this aspect of diver training. It seems to assume that the divers are right underneath their boat, or near to their exit point if they are shore diving. In real life, things are not often so tidy.

What happens if the divers are a good ten minute (or longer) swim away from their boat or exit point? What if they are near the deepest point of a deep dive? What if it is not prudent to surface immediately because of some other hazard -- e.g., boat traffic, or a strong surface current.

Over the years we have been in a few situations when we had to share air, and we have witnessed many other divers in such situations. Rarely, if ever, have these events happened right under a boat or very near to our exit point. Divers need to understand this and prepare for it, or they may find themselves in deep trouble (pun pointedly intended).

If the diver always stays very near to the boat or exit point, and doesn't go very deep, air sharing using the procedure taught in initial training, which I described above, probably will be sufficient. Otherwise, divers need to plan for -- and practice -- sharing air during a long swim, and during an ascent that may have to include a five minute 'safety stop' at 5 meters.

In order to facilitate swimming a longer distance while sharing air, one of the regulator's second stages should have a long hose. When divers are sharing air via a regulator with a 'standard' hose length of, say, 27 inches, they necessarily have to be very close to each other. It's difficult to swim while physically close to another diver, but that is what's required when both are sharing air and both are attached to the same air cylinder by relatively short hoses. It is much better to have a much longer hose on one of the second stages -- say 40 inches or even longer.

Won't a longer hose be a nuisance when not sharing air? Not really. You can do what cave divers do: bundle it and secure the bundle with a bungee cord. Alternatively, you can feed the longer hose under your right arm and across your front, securing the mouthpiece somewhere on the left side of your gear, instead of the right side where most divers stow their secondary reg mouthpiece. (Just be sure you show your buddy where it is before you begin the dive!)

By the way, if you do need to share air from a regulator using two shorter hoses, and you have to swim any distance, we figured out that it is easier to swim with one diver positioned above and a little behind the diver with the air supply. Imagine that the diver with the air source is going to give the air-sharing diver a piggy-back ride -- except the two divers swim, one a bit above the other. The 'top' diver can hold on lightly to the other diver's shoulder to maintain position and stay in place.

Now, a final note, but a very important one: practice. Practice air sharing while swimming longer distances. Practice air sharing while hovering at a depth of five meters as you would for a safety stop. (This is much easier to do if you have a regular dive partner, but even if you don't, get someone to practice with you from time to time.)

Ever since we began diving together, we have occasionaly practiced swimming at least ten minutes while sharing air. We also have practiced sharing air while hovering in place for a safety stop. We have done this exercise three or four times a year. Then one day, while we were more than a 10 minute swim from our exit point, and at a depth of about 120 feet (37 meters), a high pressure hose on my regulator popped. Oh the bubbly froth that instantly ensued! But there was no panic. Jerry passed his secondary reg mouthpiece to me right away, and turned off the valve on my air cylinder. The two of us set off toward our exit point, swimming easily together -- side by side, but with enough space between us that it was not at all awkward or cumbersome, thanks to a longer-than-standard hose length on Jerry's secondary reg. We even did a five minute safety stop before surfacing. Our practicing had served us well.

Divers, Cover Yourselves!

by B. N. Sullivan

For the past few months, virtually all of our posts here on The Right Blue have focused on interesting species of marine life we have come to know. Feedback on those articles has been positive: our readers seem to enjoy learning about creatures that inhabit the sea. But we also have been nudged by a few readers to get back to writing about diving -- as in, "Enough with the critters, already. Get back to diving stories!"

Well, okay then. How about some tips for divers?

Over the course of a few decades of diving, we have learned a number of useful things that, for one reason or another, are not taught to divers in formal training courses. The first is a simple rule that usually does not occur to divers until after they have had a bad experience or two. Cover yourselves!

In colder water, divers must cover themselves in drysuits or heavy wetsuits in order to retain body heat. But we believe that divers should be completely covered even when diving in warm tropical locations. These days, there are plenty of lightweight dive suits designed specifically for use in warmer waters.

We see many, many divers here in Hawaii -- mostly (but not only) tourists -- who seem to think that because they are in the tropics, they should just wear a shortie suit. We see them jumping into the water with their arms and legs exposed. Worse yet, some wear no dive suit at all, donning their dive equipment right over their bikinis. Guess what happens? Sooner or later, they get wounded!

It is very easy to brush against something -- a rock, a coral head -- even when you are trying to be careful not to touch anything. Sometimes it happens because the diver is not paying attention. Other times there is a little surge, just at the wrong moment. In any case, sooner or later some part of your exposed anatomy will collide, however briefly, with something in the water, and you will get cut or scraped.

In addition to those kinds of bumps and scrapes, it happens that there are many critters in the water that can bite or sting. Some are very tiny -- stinging plankton so small that you cannot see them in the water column -- so you cannot take evasive actions. Other are big enough to spot -- jellyfish come to mind -- but even then, you run a risk of being stung. Just because you see the critters doesn't mean you can count on completely avoiding contact.

The best way to prevent many of these inadvertent stings and scrapes is to wear a full suit that covers you from your wrists to your ankles. Wear boots or neoprene booties inside your fins. And wear gloves.

Now, we know that many dive operators discourage or even prohibit divers from wearing gloves. We also know the reason for that: they don't want to encourage divers to pick things up or handle them, and they figure if the divers are not wearing gloves, they may be less inclined to touch things.

Fair enough, but short-sighted. There are just too many situations where the protection afforded the diver by gloves outweighs the momentary protection of the reef and its critters afforded by bare-handed divers.

We think of it like this: we're grown-ups. We know we shouldn't recklessly handle things that dwell underwater. We know that touching corals (and many other things) can damage them. We promise we won't do that -- not because our hands are bare, but because we know better.

At the same time, what happens if we are shore diving and need to grab onto rocks at our exit point? We can very easily get cuts and scrapes on our hands, that's what.

If we are diving from a boat, what happens when we need to hang onto a mooring line or an anchor chain in order to remain stationary for our safety stop? Lines and chains that have been in the water for awhile are certain to be covered with algae, hydroids, and even teeny-tiny crustaceans. If you don't believe me, just have a look at the second photo on this page -- a 1:1 macro shot of an actual mooring line, totally encrusted with an entire ecosystem of its own! Hanging onto such a line is going to disrupt some of those things anyway, regardless of whether your hands are bare or gloved. But hanging on with a bare hand will really hurt. Said teeny-tiny crustaceans will cut your hand like little razors, and if you happen to grab onto a hydroid, you will know it, believe me. They sting like a son-of-a-gun -- and you will never forget the experience!

So then, even if you don't want to wear gloves for the entire dive, do carry a pair in your pocket at all times, just in case you have to hold or grab onto something for your own safety.

Dive like grown-ups. Cover yourselves completely to protect yourselves from scrapes and stings; but at the same time, do keep in mind that being covered (and thus protected) does not excuse you from responsibility for avoiding physical contact with the reef and the creatures that call it home.

Sneaky Shark

Caption: Why underwater photographers should have rear-view mirrors!

Where: I took this photo of the sneaky shark during a dive
at Pulau Sipadan, off the coast of Borneo.

[Click photo for larger view.]

My previous Wordless Wednesday posts.

WW #46 - In case of shark attack...

DIVER TIP: Never enter the water without one of these Hawaiian Shark Sticks!

"If attacked by shark or moray eel, hold stick vertically and insert into animal's mouth to prevent closing of jaw... If the animal should bite you, insert stick in animal's eye and push. DO NOT BLEED! This will only excite the shark or eel..."

[Click on the image to read the rest of the easy instructions.]

My previous Wordless Wednesday posts.

Wordless Wednesday home page.

Tips for diving in blustery weather

Over the years we have learned a lot of things about diving that are seldom taught in training courses. One of the things we have learned from experience is that the conditions on the surface are not always indicative of conditions beneath the surface, and vice versa.

For example, on a day that is very windy and blustery, surface conditions can be problematic or even dangerous, while conditions a few meters below the surface may be completely calm. A brisk wind can turn the surface into a froth, generate choppy swells, and create or enhance surface currents. In short, the surface of the sea is not a pleasant place to be when it's very windy.

A green sea turtle swims below the surface at Puako, Hawaii

Most wind-driven waves and surface currents extend only a meter or two below the surface, thus as divers descend they are very likely to find calmer conditions. Our first tip, then, is to advise divers entering the water on a blustery day to descend as quickly as possible to get below the choppiness and surface current. Regardless of whether you're entering the water from the shore, or from a boat, if a strong wind is blowing and the surface is choppy, plan ahead of time to get below immediately and wait for your dive partner(s) there, not on the surface.

When divers are underwater on a blustery day, they can look up and see the wind whipping across the surface -- just like in the photo on this page (taken at Puako, Hawaii) -- and sometimes the wind actually can be heard from below, too. Our second blustery weather diving tip is this: If you look up and see that it is windy on the surface, try to surface as near to your boat or shoreline exit point as you possibly can. In blustery conditions, do not plan on making a surface swim at the end of your dive. Swimming through chop and swells will tire you, and if there is a surface current as well, it may carry you away from where you want to go.

In fact, when we dive in very windy conditions we consider the rough surface to be the equivalent of an 'overhead environment.' The term 'overhead environment' commonly refers to a situation in which there is literally a barrier overhead preventing the diver from making a direct ascent to the surface. The usual examples are diving in cave, or inside a shipwreck. In the case of extremely rough surface conditions the barrier is not a physical one in the same sense -- you won't bump your head on it! -- nevertheless, we plan the dive as if there were a physical barrier. We consider that a direct ascent to the surface in those conditions is not an option, and we plan the dive accordingly.

In summary, when the surface conditions are extremely rough, it is unwise (to put it mildly) to be on the surface anywhere but right beside your boat, or within wading distance of your shoreline exit point. Descend immediately when entering the water, and don't surface until you are right at your boat or your shoreline exit point.

Fire coral: Another view

by B. N. Sullivan

Fire coral (Millepora dichotoma), Red Sea

After the previous post about fire coral was published, Jerry asked, "Why didn't you include a picture that shows what the whole thing looks like, instead of just some macros? You know, so that divers and snorkelers will know what fire coral looks like before they get too close."

I had to admit, I was remiss in not including such a shot. The photo at right is Jerry's choice to show fire coral as divers and snorkelers are likely to see it. (Click on the photo to enlarge.)

The fire coral species shown here is Millepora dichotoma. Like several other fire corals of the same genus, it tends to have whitish tips while the main structure of the colony has some color. Those of you who have been following this blog for some time could probably guess that this photo was taken in the Red Sea as soon as you saw those bright orange fishies. I've mentioned several times that these little fish, called Scalefin Anthias (Pseudanthias squamipinnis), are ubiquitous in the Red Sea.

We'd also like to note that the background color of this photo is pretty close to The Right Blue!

Fire Coral: Look, but do not touch

by B. N. Sullivan

Caribbean fire coral (Millepora alcicornis)

When is a coral not a coral? When it is a fire coral.

Fire corals (Family: Milleporidae) look like corals, and that's how they came to be called corals, although some biological characteristics related to their life cycle set them apart distinctly from true corals.

Fire corals are reef builders just like true corals. They secrete a calcareous skeleton. They take on a variety of different shapes ranging from lacy branches (like the example in the first photo on this page), to plate-like structures, to crusts that can cover other things growing on the reef, such as sea fans.

Fire corals and true corals do belong to the same phylum (Cnidaria). A characteristic that all Cnidarians have in common are nematocysts.

Nematocysts are tiny structures on the surface tissue of the organism that are used to capture food, and to defend against predators. Nematocysts actually are very cool structures -- one of nature's engineering marvels. They consist of a fine tube, inside of which is a little coiled thread with microscopic barbs on the end. When something touches the end of the nematocyst it fires the barbed thread into whatever has touched it, just like a little harpoon fired from a harpoon gun.

Red Sea fire coral (Millepora dichotoma)

The second photo on this page is an enlarged 1:1 macro shot of fire coral. The little hair-like structures on the surface (called dactylozooids) are armed with the nematocysts. Touching those little hair-like structures triggers the nematocysts to fire. Click on that photo to see an even larger, more magnified version.

The nematocysts of fire corals carry a toxin that is intended to paralyze the minute bits of plankton that are the fire coral's prey. The toxin also causes pain to predators. Divers who touch or even accidentally brush against fire coral, experience a painful sting that burns like all get out -- thus the name fire coral.

Marine biologists who study these kinds of organisms have discovered something that is useful to know. The nematocysts of fire coral (and their first cousins, the hydroids) are de-activated by acids. Thus, it's a very good idea for divers to include in their kits a small container of vinegar when they visit places where they may possibly encounter hydroids or fire coral. A little squirt of vinegar immediately stops the nematocysts that may still be stuck to the skin from firing.

Conversely, fresh water and soapy solutions actually aggravate the nematocysts. The last thing you want to do if you are stung by hydroids or fire coral is to rinse the skin with fresh water. It actually prompts any remaining nematocysts to fire.

If you are ever stung by hydroids or fire coral, you won't forget it. Usually a welt or rash arises immediately and stays for a week or more, burning again every time you take a shower or bath.

For the record, the fire coral in the first image on this page, is Millepora alcicornis, a Caribbean species. It was photographed in the Cayman Islands. The species in the second photo is Millepora dichotoma, photographed in the Red Sea near Sharm El-Sheikh, Egypt.

UPDATE: Here are some more fire coral articles and photos on The Right Blue: