|White balance works across the entire image, somewhat like a blue filter. But during the day the ocean is already doing that to everything unilluminated by artificial means. So, in any mode other than macro you will disastrously over saturate the blue sea and all those subtle blue shades beyond one metre that manifest themselves on the reef or around your subject. And that may render the acquired material, completely unusable. Adjusting white balance underwater may sometimes give good results, but you are relying on a video monitor; there will be water between it and your eye; and your brain will be subconsciously colour correcting due to the mass of blue all around. |
Trusting the camera is a classic nightmare for photographers. Moreover, with SCUBA, white balance is unbearably frustrating to set when you feel like Neil Armstrong in EVA.
There is the task of explaining to your skittish little subject that they should just hold on a sec while you stick this white slate up their nostrils and manually adjust white balance. With only about 30 minutes of actual shoot time available below 20 metres depth and with the task of finding the critter required, setting up lights, camera, tripod, stability, buoyancy, etc.., you rarely get more than five minutes on the job in any one dive.