Basic Training: Dive In! The Water's Fine! (page 2)

Your camcorder has four natural enemies: sand, water, toddlers and dogs, all of which may be present at the beach.

If you're not planning on taking your camera deep underwater, you can use something like an Ewa-Marine bag. Basically, it's a heavy-duty Ziplock bag with a glass filter attached that you put your camcorder into while snorkeling or diving to shallow depths. Their rating is about ten meters, and they cost between $250 and $350. Ewa-Marine bags limit access to the camera controls, although some models have a fitted "finger" built into the side of the bag. It's a bit awkward at first but, apart from zoom and power, you don't normally need to fiddle with too much. For your coral reef snorkeling adventure, it should do nicely. Some modern camcorders are so small you can fit them in a waterproof bag made for a 35mm camera. It's more awkward, as you have to hold or tape the glass filter to the front of your video camera, but it also means you might be able to find a used one cheap on an auction site or the for-sale bulletin board at the local dive or surf shop.

Custom housings suitable for taking your camera to significant depths can run thousands of dollars and are pricey even at the low end. The Stingray III Sport from Light and Motion retails for about $900 and will fit a number of small modern video cameras, whereas ones dedicated for high-end HD cameras can run as high as $5,000.

Depending on what you want to be videotaping, there are also dedicated systems such as the Aqua-vu (www.aquavu.com), which is basically a steerable, fish-shaped (no foolin'), underwater security camera designed for fishermen and people who are curious as to what's at the bottom of a lake but don't want to get wet finding out. The camera trails behind your boat on a cable, investigating the briny depths. The cameras range from about $250 to about $2000, are available in color or black-and-white and will interface with a recording device.

People love to be in and around the water and they love to watch video. It makes sense to bring the two together and share your underwater activities with others. Your camcorder doesn't belong underwater, so you'll need to keep it dry. There is a variety of commercial devices that do this, from bags to hard-shell cases.

Kyle Cassidy is a visual artist who writes extensively about technology.

With depth comes pressure; the weight of the water above squeezes things beneath it. For this reason, something that's watertight on the surface will leak (or even crush) at depth. Things that go underwater, like wristwatches and camera housings, are rated to a particular depth. Static pressure is different from dynamic pressure, meaning that, while a case may be watertight at 40 feet, the pressure might actually be the same as being at sixty feet if you move the case quickly through the water. (Fashion wristwatches, for example, are usually rated for static pressure, which means you can lower one slowly on a string to 100 feet and it might not leak, but if you put it on your wrist and swim with it, it will quickly fill with water.) As a general rule, don't take anything snorkeling (your watch included) that's rated for a static pressure of less than 100 meters.

Also, salt water and fresh water have different densities; salt water is heavier. This means being 50 feet down in the ocean is not the same as being 50 feet down in Lake Gitche Gumee. Professional equipment is rated either FSW (feet of salt water) or FFW (feet of fresh water). If you take a camera housing rated in FFW into the ocean, you could end up with a wet camcorder.

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