Ok, maybe not a boating issue but it might help you someday.
My wife was going up the ramp from the dock, tripped, grabbed for the railing, saved herself but the car key in her hand did an Olympic dive for the water. It was on one of those float things. It was a remote key fob and it was hanging from the float. Although the float was on the surface, the key was hanging from it completely submerged in salt water.
I went to the boat, got the boat hook and fished it out. It was submerged for about 3 minutes. I shook it dry as I could and then tried it. It was totally brain dead as expected. Here's what I did, with low expectations but it worked!
1. Remove battery and dry the key as thoroughly as possible by shaking and wiping with paper towel. Discard the battery.
2. Place the key on top of a cable TV box (which is warm) and leave it there for 2 or 3 days.
3. Thoroughly spray the key with Corrosion-X or the like getting the spray into all the crevices you can.
4. Dry thoroughly after 10 minutes by shaking and paper towel.
5. Place it back on the cable box for a day or so.
6. Install a new battery
7. Try using the key.
8. If it doesn't work, go to the internet and search programming the key for your car's year and model. Follow the programming instructions carefully.
My key works perfectly again!