I'd check the IP rating as already mentioned, but I have a Lowrance on my kayak. The navigation card slot has a rubber seal but I have made it extra water proof with some DIY tape. As for the connections, it is best to fill them with dielectric grease, don't worry, the connection will still work. This prevents corrosion on those points. I also spray some lanolin on the connections after each trip. It has copped heaps of salt water spray. I hose down the whole thing each time and haven't had a problem in 2 years, no sign off corrosion. You also have to worry about electrolysis or corrosion travelling up the wires from the battery, so also make sure that is completely sealed in a water proof case of some sort. I made my own with a switch on it, also contains a fuse.