Carrying in and around water?

[Mr. 16 gauge]

From my earlier reference in the handgun thread....

I am primarily a duck hunter. In the area that I hunt, border patrol has had a lot of issues with illegal aliens coming through the marshes. Also, some of the other "hunters" are what I would deem a bit on the "socially undesirable" side of the coin.
Anyway, I am looking for opinions/thoughts re: carrying concealed in and around water. What type of firearm, what type of holster, holster material, ect.
Some of the problems are: rust, getting access to the gun quickly, and making sure that the gun doesn't rip my waders........cold water/hypothermia can kill rather quickly. I have a shotgun with me (obvioiusly), but during transport the gun must be in a case, and I keep mine in a floating gun case just in case the boat tips and gear goes overboard.
Anybody out there have experience, like Marine sherriffs patrol or some such thing? I carried my S&W M39 out while salmon fishing a few years back.....the perspiration from wearing neoprene waders caused the gun to rust quickly; I was quite upset. Stainless steel or nickle? I'm thinking leather holsters are out, because of the chemicals used for tanning, if wet, will speed up rust.....what about Kydex? Also, I'm worried that carrying on the hip will cause the gun's exposed hammer to tear into the neoprene, causing a hole. Shoulder carry is probably out, as there are too many straps, buckles, ect. with the waders, ammo carriers, duck straps, ect.
I know, it's a tall order to fill.......but I think my knowledgable group of friends here on HUNTCHAT can help me out.......please?