On Tuesday we talked about underwater white balance, what it is and how you can do it. If you recall Step 2 of the process,
Point your camera at something you know is white and "take" a picture or press the appropriate button. The camera will record your settings.
This is potentially a problem. How many pure white objects are there in the ocean? Much less one that is a nice flat surface for setting white balance.
If you're even semi-serious about getting good underwater pictures with your point-and-shoot, I recommend picking up a dive slate. Usually used for communicating via writing underwater, a dive slate makes for a nice flat, white surface perfect for manually setting white balance.
As a side bonus, slates are inexpensive. They often have a buckle or strap of some sort to attach to your BCD.
A dive slate is a useful gadget to have anyways, but becomes indispensable when you need to set white balance.