I'm guessing this might have been covered at some point, but I am pretty much clueless on how to search... I'm curious to get some feedback on the following idea:

I have a dock on our 12 acre lake which I ran power to when we built our house (double outlet GFCI) for running lights, battery charger for the john boat Etc. My in-laws live across the cove from us and have a boat house roughly 200 feet from our dock. My father in law would like to run power to his boat house (also just for lights / battery charger), but in order to run it from his house we would be looking at trenching through about 200 yards of dense woods (not fun). The water between my dock and his boat house does not exceed 6 feet, and we are the only people who use the lake for what it is worth.

What I would like to do is run power underwater from my dock to his boat house, but being at best a weekend electrician I am not sure if this is a smart / practical idea. I would sure appreciate any feedback you all might have to offer. Thanks!

- Cullen