Re: Best handgun for a corrosive enviornment?
Not a huge Glock fan, but I'd have to say that would likely be the most suitable pistol for his use. If he wants a revolver, I will second the above recommendation of a Ruger GP100. Of all the grades of stainless used in firearms, I have been the most impressed with Ruger. My Smith 686 was always getting little "freckles" of rust when I lived in Florida. My GP100, Super Redhawk, Bearcat, P90, P91, Vaqueros, and various rifles never had this problem, despite carrying some of them on my boat.
No matter what your dad decides on, a couple layers of a quality carnauba wax will keep the exterior in pristine condition (no moisture or oxygen in contact with the metal = no corrosion). Flitz makes a great gun wax or you can use any good automotive carnauba...just make sure it isn't a "cleaner" or "polishing" wax. That means there are abrasives in it.
Or you could use a HiPoint. They're gawdawful heavy and the slide is made of zinc, so it can double as a sacrificial anode and an anchor.