It also occurs to me that depending on what amp you are using you might experience some salt air problems there.

Basically, I would not use an open back tube amp often and regularly in that environment, particularly an expensive one. There's just too much wiring involved and the risk of failure. To me, its just too high to risk it. And since you are not primarily a guitarist, you have many acceptable options.

What I would do is use a decent solid state, preferably closed back cabinet amp. They are many options. They are less expensive and they can give a great sound. It would isolate as much as possible from the salt air and remove the tube wiring circuitry risk. Its not like a top of the line tube amp in all regards, but not bad at all.

I have to say that in some of the places I've played using the solid state JC-120 was way way better than risking a Fender Twin Reverb.