We digital underwater photographers struggle a lot with sunballs underwater (a "digital bummer," Berkley White says). While diving Blue Corner the other day, I shot the best digital sunball I've ever taken.
anemonefishes aerate and guard their eggs
Shot details: Canon 1Ds Mk II with a 16-35/2.8L lens @ 16mm, 1/200 second @ f20
Depth was about 60'. I think one of the main reasons the sunball is so good is that the surface of the water was a bit ripply, which broke up parts of the path from the sun to my lens.