"You're already screwed. You looked at it. '

You got that right. People think we have some eye power like Superman or something.

Actually an isolation transformer would work, but there is nothing to indicate an insidious fault. All it takes is enough static electricity like during a thunderstorm striking nearby or something and it no longer isolates.

So it would be wise to use a GFCI, and then of course you don't need the isolation transformer.

Circuit breakers and GFCI outlets are designed to minimize the possibility of a no trip failure mode. No such thing in an isolation transformer. It could make it worse actually.

I would still recommend a low voltage alternative for the lighting. And a GFCI because when you are all wet you can get a shock from 12 volts. Probably not lethal directly, but could prevent you from getting your head out of the water or something.