Getting into underwater photography can seem daunting at first - you may visualize a lot of additional gear to lug around, handle during the dive and properly maintain between dives. However, Olympus makes a great series of cameras that allow you to dip your toes into the hobby without overwhelming yourself initially with the price tag or extra gear. One of the latest in the Tough series line, the TG-4, is a compact camera that is waterproof out of the box to 50 feet and rugged to stand up to less hospitable environments. If you plan to exceed the 50 foot depth limit Olympus makes a housing for the TG-4, the PT-056, that is capable of 150 foot depths. Without the housing, the camera easily fits into a BC pocket; with the housing it’s still small enough to clip to your BC easily when you need both hands.
Shooting ambient light only (i.e., using natural light and no strobes) works very well at shallow depths when using the available underwater modes of the TG-4. The underwater modes (for wide angle and macro) automatically perform white balance adjustments to account for the effects water has on light. With the camera in the PT-056 housing, the flash diffuser will soften and spread the light from the flash and allow you to get colorful macro and closeup shots, as long as you remember to get close to your subject. As you get more comfortable with the gear and the hobby, there are an abundance of accessories you can add to your TG-4 to expand its capabilities.
When you’re ready to start using a strobe to ensure colorful and vibrant photos as you go deeper, a simple but great option is the Sea & Sea YS-03. It’s TTL (through the lens) only, which means that the output of the strobe is determined based on the TG-4 reading the lightness or darkness of the scene you’re shooting. This means you won’t have to worry about manually adjusting the strobe output for the correct exposure. I’ve had good success shooting TTL with my TG-4 and getting proper exposure but if desired, strobes with manual control are also available. There are also wet lens options that mount to the 52mm port of the PT-056 housing. The UWL-04 works great with the TG-4 for shooting wide-angle scenes.
Whether you want an easy camera to bring snorkeling, a simple housed camera for diving, or a compact rig loaded with accessories, the TG-4 is a great camera for getting acquainted with underwater photography. Below are a few recent shots with my TG-4 rig and for more on underwater photography with the TG-4 see my blog
emeraldcoastunderwater.com 
Mala Wharf, Maui (TG-4, YS-03, UWL-04)
Navarre Reef, FL (TG-4, YS-03)
Destin Jetty, FL (TG-4 internal flash)