To avoid hot spots caused by focus lights, increase shutter speed to reduce the effects of ambient light. With my particular system, I don't shoot slower than 1/125 sec at night.
There are systems that will automatically shut off the focus light at time of image capture.
The focus light at night does not have to be white. I use a small, 4AA light which emits a red beam to aid in focus lock. I place a thin piece of Roscolux red gel #027 on the interior of a UK mini Q 40, between the lens and the reflector. Roscolux films of various shades can be purchased online or at a local theatrical supply store.
I still rely on the modeling light of my Ikelite DS 125 for navigation and search of interesting subjects. But many of the critters that come out at night are very light sensitive, therefore the red focus light. Once a subject is identified, the modeling light is turned off. The red beam then allows me to approach crustaceans and capture them with their eyes still open as opposed to squinted or shut as a result of a relatively blinding white light in their eyes.
I would test in a pool first to insure that your particular camera can achieve focus lock with a red beam. I do know that the Oly c4040 and c5050 can.