I've given this some thought the last few days (too much time on my hands). Considering it's only 1 pistol.. I would carry either an N-frame .357 4" or Redhawk 5.5" stainless .44mag. I own these and it would be a difficult choice leaving the various Glocks behind, but I wouldnt want to mess with plastic auto pistols in swamp or rugged conditions at least not for very long..
Given my druthers, for swamping a rifle-sighted 12 ga shotgun would be paired with the revolver, the problem there being ammo weight. Maybe a 20 ga, but the ammo and barrel choices would be limited. A marine shotgun would be in order for the swamps, too bad no one makes a stainless shottie (that i know of). Of the shotguns I actually own, a Mossberg 500 set up for police use would be my choice. If it got ruined no great loss as it was a dept weapon that retired with me a few years ago.
In a non-swamp environment like the western hills and plains of course a rifle would be in order, maybe my Mauser hunting rifle in 8mm or my BLR .308 (ouch, the thought of beating on it makes me cringe)... While it isnt the most modern weapon, the '98 Mauser has been proven in many wars and skirmishes and would do in a "survival situation" as discussed.
Fun thread- thanks for posting it!