Perhaps the most important difference you’ll find in taking pictures underwater is that water absorbs and scatters light much more than air and selectively filters the colors from light that enters it: the reds and yellows are removed first. By the time that you reach a depth of about 20 feet (even in very clear tropical water), the image recorded on film with natural light will be a blue-green monochrome. Bearing this in mind, here are some important guidelines:

• Get as close as you can and then try to get even closer. For beginners if you can’t touch it you probably shouldn’t try to photograph it. All underwater photography is actually about this: either macro (close-up) photography of small things or extreme wide-angle photography of bigger subjects. In which case you are still very close, but the wide-angle lens covers a large area. For those just starting out, a camera set-up with a close up lens and a small strobe can produce some very impressive results.
• Bring your own light source. For underwater still photography, some sort of strobe or flash is a must.
• Dive under control. You should have your buoyancy concerns resolved and know your limitations before adding photography.
• Use the right equipment: disposable underwater cameras are fun to try if you are snorkeling in clear, bright tropical waters, but even under these conditions, they have their limitations. Otherwise it’s worth buying or renting some better equipment and getting some help in learning how to use it properly.