If you're starting from scratch, getting into the right underwater digital camera system will require a little soul-searching. Your first question should be, "What kind of images do I want to create?" Are you looking to capture memories of your dives, or do you have secret ambitions of becoming a pro shooter? Are you looking for easy-print snapshots or wall art? Once you determine the kind of images you're after, then it's just a matter of finding the right tools to the job.
Digital SLRs are the big-boy systems that make tec geeks drool. Housed in sophisticated boxes that cost as much as or more than the cameras themselves, they are typically adorned with long gangly arms and fat underwater strobes. The benefit is that with a good dSLR, housing and strobe combination, the sky is the limit. With optional ports and the ability to use different lenses, you can create stunning, high-resolution images of everything from seahorses to blue whales. And you'll be able to put your photos in nearly any size format. This is the high-road option, and it calls for a financial commitment that starts at several thousand dollars and has no real end in sight.
For a middle-of-the-road approach, there's a slew of high-end point-and-shoot cameras. Their primary physical difference from the dSLRs is that the camera body will not accept different lenses, and everything (lens, camera, flash) is in one compact package. What separates these machines from the truly simplified point-and-shoot cameras is a combination of megapixel capability, options for external strobe lighting and level of control over camera functions. Megapixels translate into higher-resolution images and greater flexibility in output into different formats. External strobes are a must to consistently bag good images in a wide range of water conditions. Also, look for the ability to shoot on manual or with aperture priority exposure settings so you can be in complete control of what the camera is doing. Finally, before you buy, determine what housings are available for your preferred camera and make sure they accommodate strobes, arms and synch cords. Your cost should stay inside the several-thousand-dollar range.
For the bliss that comes with pure simplicity, go with a true point-and-shoot camera. It's amazing how many manufacturers are making underwater housings (most rated to 100 feet or more) for their compact digital cameras. Most cameras have preset shooting modes to take the pain out of figuring exposure values, and most will capture short video clips. The details to be picky about include the size and readability of the camera's LCD screen, available memory-card formats and power sources. Rechargeable lithium-ion or nickel metal hydride batteries will last a lot longer than basic AAs. Many models also allow a direct hookup from your camera to a printer for super-simple photo production. You can have all of this for $1,000 or considerably less.