Considering the power of those switches to bering an entire boat to a grinding halt, they are ridiculously bad at letting water in....
I made myself a short jump lead and used the spare nuts from the terminal posts of the dead switch to allow me a quick "bypass" if required. The spare nuts are above the ones holding the batt etc leads in place, and means i can add the jumpwere without all the wiiring falling off.
Of course by doing this I have ensured the current switch will last indefinitely.....