There are two types of underwater camera systems: an "amphibious" camera, which is a self-contained waterproof system, and an SLR land camera with waterproof housing. Amphibious systems are small, compact, and easy to travel with, while SLRs offer more advanced features, such as auto-focus, advanced exposure control, and through-the-lens viewing.

The "amphibious" cameras are probably best for those of you who want a simple, easy-to-use point-and-shoot camera. Amphibious systems usually have a built-in lens and they will take pictures on land as well as underwater. They also have an automatic film load and advance and are generally compact, lightweight, and rugged.

If you are a more serious photographer and want the advantages of a single-lens reflex camera you will probably be happier with a land camera in waterproof underwater housing.

As a new underwater photographer you need to know the difference between taking pictures on land and underwater. The difference is what you are shooting through to take the picture. Air is transparent, whereas water is not. Light does not travel in a straight path underwater like it does in air. Water is denser and it includes particles of sand, plankton, and other debris which scatter, reflect, and absorb light.

You should know that all your underwater equipment needs and requires special care. Salt, sun, dirt and improper storage can damage a camera. Even though all your new stuff is made from rugged materials built for underwater use, it still needs to be rinsed in fresh water after every use. Saltwater should never be allowed to dry on the joints of the controls and metal fittings. Salt is your system's number one enemy. Do not rinse with a hose. The high pressure may actually force salt crystals and sand into crevices. Use only soft lens tissues or photographic lens cloths on the lenses.

The most important thing you need to know about your underwater camera care is how to clean and lubricate the O-ring after every use. The O-Ring creates a watertight seal to protect your equipment from water, and so it is very important. The seal must be flawless— with no scratches, cuts, sand, hair – nothing on its surface. If it is not, the underwater photo equipment will be ruined. Water must be kept out! When in doubt about the sealing capability of an O-ring, always throw it out and replace with a new one.

Both your camera and your flash will need a watertight housing. You can use a flash fill-in to brighten underwater subjects at close range. Even with large flash units, though, light does not extend beyond 12 feet. The maximum effective distance of most flashes is four to five feet. Subjects farther away will not appear very colorful. Don't forget you need to wait for your flash to recycle.

Assess conditions underwater before you dive and set aperture and shutter speed before entering the water.

The best time to take pictures without using a flashgun is between 11 a.m. and 2 p.m., when the sun is overhead. To capture sunrays with the subject in silhouette, face the sun. Close-up shots of fish are best taken at night--the fish are sleepy and not as active

Shallow water near steep rocky shorelines, coral reefs and atolls, and areas near tidal streams are great places to photograph sea-life.