A good practice is to open your radio box after each outing to let it air out. Moisture does accumulate in the box after time on the water, no matter how water tight you think the box is. Another phenominum that can occur is called "Black Wire". Its basically corrosion of the wires in the radio system. Especially the battery leads. It never shows up until the boat is running it's best. Then, for no know reason, you loose radio contact and the boat heads for the nearest rock as you watch helplessly. Investigation will reveal black corrosion on very brittle wires once you strip back the insulation. If, on the other hand, your system is exposed to the water, then you can thank yourself for being so dumb as to invite corrosion and water infiltration into the system components.