The biggest effect that water has on light is to gobble it up. Underwater lighting needs to be very powerful to get anything out of it. Everything tends to take on a cyan cast, and colors can alter a bit, but other than that, the boundaries are set by equipment limitations. I’m frequently trying to simulate interesting-looking lighting that I see on the surface and trying to adapt underwater strobes or lights to see if I can make a similar effect underwater. My shoots normally involve quite a bit of rigging to get lights exactly where I want them.
There are other problems shooting underwater; mostly to do with camera equipment and water not mixing. If something’s leaking or you’ve got a drop going into a cable at one end, you’ve got to find out what’s not working. It’s particularly problematic if you’re using three cameras and three cables.