Finding Shells Underwater

by B. N. Sullivan

I have been collecting seashells since I was a little girl. Early on, my collecting was limited to shells I found washed up on a beach somewhere, but once I learned to dive, I began looking for shells underwater. Later, when Jerry and I began to dive together, he took up the hobby, too, and over the years, we have amassed quite a respectable shell collection.

We are purists about shell collecting. As I mentioned in the previous post about shell collecting and diving, we do not buy shells, and we do not sell them, or even trade them with other collectors. All of the shells in our collection have been found by one of us.

We also are purists in another sense: we do not take 'live' shells -- that is, shells still occupied by anything living, whether it is the snail that originally secreted the shell, or a hermit crab that has adopted the shell as a home. I cannot say that we never have been tempted to take a live shell; of course we have been. But we don't do it because, over the decades that we have spent in the ocean as divers, we have witnessed a noticeable decline in the number of shells that we see. We know that one of the reasons is that collectors -- and dealers catering to collectors -- have repeatedly harvested live shells before the critters that live in them have had a chance to reproduce.

Many popular dive areas around the world officially prohibit the taking of shells, live or otherwise. There was a time when this kind of rule was encountered only in officially protected areas, such as marine parks or preserves. Nowadays, many dive operators and resorts (and even some municipalities) prohibit divers from collecting any shells, including empties. These 'no-take' rules may seem extreme to some, but in many cases they have arisen because divers (and other people) were taking shells indiscriminately, including those still occupied by their natural residents, and populations were becoming seriously depleted. If you dive in an area that prohibits shell collecting, do follow those rules.

Shell collectors should be conservation-minded, even in areas where collecting is not officially prohibited. We have witnessed plenty of instances of egregious over-collecting. For example, one time we saw a diver climb aboard a boat, carrying twenty-some Marlinspike Augurs (like the shells in the photos on this page). He proudly announced that he had spent his whole dive digging in the sand for them. All of them were alive. Another time, a diver waded ashore with a very large glob of mucus oozing out of the pocket of his BC vest. It turned out that he had collected several large, live cowries and had stowed them in the pocket. In both of those cases, other divers in the party confronted the poachers. The man with the Marlinspike Augurs tossed all but three overboard; the man with the cowries kept his shells, casually announcing to us that "the animals are probably dead by now anyway."

Divers are not the only ones who sometimes engage in excessive collecting. Early one morning as we were preparing to enter the water for a shore dive, we saw a woman sitting near the edge of the water beside a plastic bucket. As we walked past, we were horrified to see that the bucket was half full of assorted cowries. We asked what she was planning to do with all those cowries. She told us she was waiting for the sun to kill them so she could "scrape the muck out of them" with a penknife. She said she had collected them the evening before, while wading in the shallows. It turned out she was a tourist, staying at nearby vacation rental cottage. She told us she did this every year when she visited Hawaii, because she liked to take the shells home to her friends as souvenirs.

As collectors ourselves, we obviously have no quarrel with taking shells, but we do promote prudence in collecting. Don't take live shells; and learn to be satisfied with collecting one or two examples of a given species. If you find a handsome shell that is occupied, do photograph it, but please don't deprive the poor little guy inside of its home.

How to Find Shells

Our success as collectors has grown from an understanding of which critters live where. If you want to collect shells, the first thing you need to do is learn something about the mollusks that create the shells. Learn which kinds live where -- in sand, in rocky rubble, among coral -- then you will know where to look for them. It also helps to learn what they eat. You won't find them where there is no supply of their preferred food.

Learn which other animals eat the snails that inhabit shells. If you discover where a mantis shrimp lives, for example, you may find a small cache of empty shells near the entrance to its burrow (although many will be broken). If you notice an octopus hunting, follow it for awhile and you might be rewarded. We once acquired a large tiger cowrie shell, compliments of an octopus. We watched as the octopus enveloped the tiger cowrie with its body, sucked out the poor snail, and then dropped the empty shell onto the sand. We still have that shell, thank you very much.

Another strategy is to take note of places where empty shells tend to collect naturally, due to the forces of waves, surge, and currents. In reef areas, small conglomerations of shells often can be found near the base of large rocks or coral heads. In inter-tidal zones, waves and surge will carry empty shells along and deposit them among the rocks. Sometimes shells are buried under a bit of sand, so a good technique to use in a likely area is to wave your hand to fan away the top layer of sand to expose the shells.

When you find a shell, how do you know for sure if it has a creature inside? Sometimes it's very easy to see if a shell is empty. If you pick it up and a lot of sand pours out of it, usually that means it is unoccupied.

If you find a shell with its opening facing upward, it probably is not alive, since mollusks and hermit crabs that live inside shells typically move along with the shell on top of them. But the aperture-up rule is not foolproof. Finding out if there's anybody home inside mostly takes patience. You need to leave the shell, aperture up, undisturbed for awhile -- sometimes for as long as 10 or 15 minutes. Wait, and eventually an animal living inside -- whether a snail or a crab -- will poke out, or even try to right itself. The second photo on this page shows that the Marlinspike Augur, which looked to be empty at first, actually had a tiny hermit crab living inside.

Coming up: more stories about certain types of shells and the creatures that live in them.