I just added a new article on using a waterproof digital camera and it is definitely worth a read.
Unlike land photography you have to be more mindful with lighting underwater. Underwater colors will dissipate with depth due to light refraction. Often times underwater you will notice that colors begin to turn gray as you go deeper underwater. Many colors will lose their vibrancy, while others can be more distinct. Red tend to appear better when snapping digital underwater photos. In tropical locations yellows, reds, and greens can be eye catching because reefs are shallow allowing more light to reach the reefs and fish.
>>> Read more at the full article on using a waterproof digital camera