Should following a normal "custom" white balance process while at depth > result in accurate color capture? Any special considerations?>

Yes...but be aware that there's not always something around that should be> white, or similar to a grey card unless you take something with you. In fact> in blue tropical water I've often had better results taking a reading off> the palest sand I can find on the seabed instead of using a white slate.> With this method you can also often get a reading from the sand where the> latitude of the camera isn't enough to get a reading from the slate. If in> doubt try it and see what the result is like.>

Stan