The great majority of "nuisance" tripping is the GFCI working like it is supposed to and the electric drill or whatever is leaking to ground! I have seen many instances of bad equipment and blame goes to the GFCI. Salt air will corrode most anything over time but salt air won't support an arc much more than fresh air. Seawater or damp salt deposits are another matter. Brian brings up a good point about testing your GFCIs with a listed tester or at least the little test button on the recept. monthly. A fellow was badly shocked and damn near killed at my last workplace from a faulty GFCI.