It might be worth looking at having the barrel treated (TiN, DLC?) in the first Glocks the barrel was tennifer treated too, but I'm guessing that they've stopped that. Someone must make a stainless barrel? Given the purpose you have for the firearm, there are few other end users that see the same environmentals, might want to see what the Navy guys in the States were doing before the GWOT, at that time they were more concentrated on water ops than they are now. I've heard military folks of that era complain about Sig springs failing due to salt water exposure, so I'm not sure what the answer is to those problems other than what Sig did with the "Navy" guns. Interesting to note that the first handgun issued to Seal Team 6 when they were called that, was a Smith 686, specifically due to it's ability to shrug off salt water exposure and continue to function.