For sure! I was planning on holding the exposed wires in my teeth while I jumped in to the water to set it up - with it plugged in, of course.
The plan is to mount the box on a piling that is under a roof, run the extension cord that runs to the light down through the dock and out to where the light will sit. All of the cord that will be submerged is run through the water hose and is sealed off by marine/through hull sealant (and concrete on one end) as another layer of protection against fish hooks.
Thanks! I thought about the potential for snags too, that's why I thought about the fish bowl instead of a cage. The spot where the light will sit isn't too far from where kids jump in the water and they can hit the bottom when the water is down, so I'd rather not have glass on the bottom if the light were to burst. It's probably overkill though.
Thanks again for the idea, I never would have thought to go this route without your suggestion. Total cost of materials was less than $50, but I already had some stuff - extension cord, hose, box for the ballast, etc.