The Basics of Underwater Photography
Before you purchase your first underwater camera, you should evaluate what types of photographs you want to shoot. It will be an essential point when selecting your underwater camera equipment and film. Underwater photography can be broken down into four broad categories: general, macro, wide-angle, and fish photography. Each category involves a different camera configuration, flash and lens. Sometimes you’ll have to plan your dives to complement your intended type of photography. Most of all, you’ll want a camera that is: compact, easy to use, low maintenance, reliable, and cost effective.  Then you will have to decide between a digital or film camera.   A good article is:  Taking Underwater Photos - The Basics

General Underwater Photography
The majority of underwater cameras are made to shoot general photography. It doesn’t involve much more than the camera itself. Various point-and-shoot cameras have a fixed focus at a specific distance. Therefore, the subject is sharpest at that focus point. With general photography, you can take pictures of underwater scenes, other divers, or both. Many of the compact cameras have a built in flash for convenience with a maximum distance of seven feet, but many manufacturers offer a more powerful flash as an accessory.

Macro Photography
Close-up photography is the easiest and most vivid type of underwater photography. The best method of capturing small creatures depends on the camera system you use. Most cameras have close focus limits so you will need a special accessory to allow macro photography. Several of the point-and-shoot cameras have a macro lens and framer system. When you want to take a close-up picture, you attach the system to your camera, place the framer around the subject, and click away. Use a flash to bring out the color of your subject. Look for a camera that will allow you to attach the macro framer while underwater.

Wide-Angle Photography
An exhilarating facet of underwater photography is the ability to capture a panorama of a reef and its ecosystem. Wide-angle photography makes this possible. Clearly, a wide-angle lens is needed for this type of photography. In addition, powerful strobes are desirable because the field of view caught on film is greater and needs to be lit. Wide-angle photographs are best taken with wide-angle specific lenses.

Fish Photography
Fish photos are great, but they are the most difficult pictures to take. Fish don’t sit still and they don’t let you get close. To capture them on film, a special approach is needed: stealth, knowledge of the fish, and patience. Clever systems for novice cameras use gun sight viewers or light beams to let you know when the fish is in your frame of focus. It’s a hit and miss process, but practice makes perfect.

Film
Color negative film is great for new underwater photographers. It features a large selection of speeds. Also, it has a wide exposure latitude. This means the film has an excellent margin in its ability to give a correct exposure despite varying levels of light. In other words, you’ll get a good picture, even if your exposure wasn’t quite right.  Some photographers recommend using Fuji film in the Caribbean due to the green tint in the water and Kodak film in the Pacific due to the blue tint in the water.