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.