Tropical Ecology: Snorkelling

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Updated: March 7, 2001

See the Underwater World:

My research at La Selva for the past five years has been on the fishes and so, if you are interested, you have the special opportunity on this trip to see a side of La Selva that few others have seen, namely the fish. This is optional but I strongly encourage you to consider it because we will be at La Selva at an ideal time to observe fish spawning and parental care behaviour. It is something that you are unlikely to ever experience otherwise.

This is not like snorkelling on a coral reef: the river is fairly shallow (less than two meters in most places), has a moderate current, and visibility ranges from fair to poor. But, in it are hundreds of cichlid fishes, doing what they do best, namely raising their families of kids.

This is my area of expertise and I am happy to show it to you.


The downside of working on fish, or wanting to see them, is that you need a bunch more stuff than you would need otherwise. Namely, you need snorkelling gear. There is no diving -- the river is too shallow and dive gear would only get in the way.

To take part, you will need a bathing suit, mask and snorkel and fins. Plus I strongly encourage you to bring a wetsuit of some kind.

The mask is the most important thing. You want one that fits. There are many brands and models of masks and the trick is to find one that fits the size and contour of your face so that it does not leak. One way to test this is to put the mask on your face (be sure there is no hair under the seal) without putting the strap around the back of your head. Now inhale gently through your nose and let go of the mask with your hands. It should stay in place. Guys with moustaches have a particularly difficult time and may have to put some vaseline on the moustache to get the mask to form a good seal.

Any kind of snorkel will do. I prefer the old-fashioned, J-shape without any valves, gizmos or contraptions. It is almost impossible to find one of these anymore. The new snorkels have drain valves, baffles, etc all of which are unnecessary (but they look cool!).

Any kind of dive fins or snorkel fins will do.

The reason for the wetsuit is the following. The water will be between 22 and 26 oC, so it isn't very warm. Most of the river is shaded by overhanging trees. The water is moving constantly, and pulls the heat out of your body much faster than does a lake. I wear a regular 1/4 inch (6 mm) neoprene wetsuit.

I have had people go snorkelling with me without wetsuits. After two hours, they come out a rather intense shade of purple. Every such person has said it was fabulous and they would do it again but they really wish they had a wetsuit.

Even a wind-surfing suit would be better than nothing. The color of the wetsuit is unimportant. You do not need or want mittens or a hood, just johns and a jacket and booties. Booties with a hard bottom sole are the best.

Also, a wetsuit provides buoyancy, which is helpful if you aren't an Olympic-class swimmer -- I am definitely not a strong swimmer, which is ironic for someone who works in the water.

Hint: If your wetsuit is a snug fit, many women find that wearing an old pair of pantyhose helps the suit slide on much more easily.



Game Plan:

River snorkelling is quite unlike any other kind of snorkelling. The river moves too fast to swim against and at first this can be a little disconcerting. BUT, the cool thing is to realize that there is always a shallow spot downstream where you will get washed into and where you can easily stand up and walk out. Don't fight the river -- work with it and you will see amazing things.

A typical snorkelling run is done by walking up the trail which follows next to the river. This takes about 15 minutes. Then we get in the river and drift downstream exploring the area near the banks which is where the fish are. We end up drifting right by the "River Station" of La Selva where we get out at the stairs and walk up to the showers (which have hot water -- you cannot beat this arrangement anywhere in the tropics).

It can take as little as half an hour if you hurry, or as long as 3 hours or more if you take your time to explore thoroughly.


River Hazards:

The river is surprisingly benign. For example, there are no water snakes! The only thing that could potentially hurt you is a caiman -- small relatives of crocodiles. I have never had any trouble with a caiman and they aren't common. I suspect you would have to stick your fingers in a caiman's mouth to get it to bite you. Of course, if someone stuck their fingers in your mouth, you'd probably bite them too!

While I am one of the few people to do research in the river, just about everyone else uses the river for "floating" -- riding an inner tube along the same course we travel. It is a favorite form of relaxation and no one has ever had any trouble with a caiman.

The biggest hazzard from snorkelling is that you will be captivated by what you see and want to spend the rest of your life studying fishes. This disturbs many parents who had plans for you to become a dentist. {The last time I offered this course, I took a young woman into the river who had a phobia about small fishes; now she is applying to graduate school to study them}. Consider yourself warned!


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