I have not had any problems with mine. It is mounted high up near the top of the fire wall.
I would have to submerge the engine to submerge the fuse block and I am not running a snorkle so I hope that does not happen. I have my OR lights, OBA and amp running off of mine.
Unless you mount it on top of your roll bar you are not going to find a much higher point to mount it. Remember, Your computer that is not water proof is in the same location on the other side of the firewall.