Thats just like asking which scalple does the the best open heart surgery! When its really all about the surgeon's skill. There are factors effecting sunlight pictures underwater, cloud cover, wave action, depth, water clarity etc. In regard to the camera (a tool) it must have a SPOT metering function, in order for the photographer to accurately meter the correct fstop settings. The sun's center stop maybe around f32 and points away from the sun could be f4.0, a BIG difference in exposure!
Now here is where the skill part kicks in. If he shoots at f32 the blue water turns black and the sun looks like a flashlight in the dark, so he then shoots at f4.0, the sun turns into a super nova blow up of white/light blue, the points at the edge of the frame looks ok. Here is where the "B" word for bracketing comes in, shoot from f16, f11, f8 etc. and pick out your best shot! Now in the age of digital cameras he can review his shots on the spot, life just got much easier!
The question does bring up a sad fact that some folks (not all) are just getting in to U/W photography when they do not even know the basics on above water photography. Then thinking that the latest hi tech camera will be their magic bullet!
Sidenote: This is the reason for my big push on LARGE Bright LCD displays I have to see all that info. before the shot is taken. The 8080 LCD is too small, I may need to get a 4 inch TFT LCD display and make an external housing for it.
Dive Safe