Computers can be slightly moisture resistant, though. We put a Zip-Loc bag over the computer to block moisture, and use the stylus right through the bag. If the computer could be damp on the inside at the end of the day, backup the memory, remove the main and backup batteries, and leave the computer in a dry area for a day or so. Salt spray should not be allowed to get on the computer. If it does, it should be wiped off with a fresh water dampened cloth to prevent salt from getting inside.
Salt is major enemy of electrical contacts. .