I use my G Quest on my bike off road and in my bass boat. I did put it in my small boat for use in the Knysna lagoon to try log the exact chanels but there is not constant salt water splashing on the unit.
I have also used it on my fishing ski off the coast at Port Edward but it was housed in a waterproof container and then when out of the surf I used it there. Before heading back to shore I store it away again.
I would be reluctant on a ski because of that very reason.