Air pistol
Chuck dropped me a PM that someone had an airgun question. I'll take a shot at an answer, but first allow me to ask a few things and make a few observations.
You hinted that the gun might spent some time in a wet bilge. Would you do that to any of your target grade guns and expect them to maintain their accuracy? Being of almost all brass construction, most notably the barrel, that requirement points to either Benjamin or Sheridan multi-pump pnuematics or CO2 guns. Neither of which are big fans of water and silt. Either make of either operating principle would be up the tasks you pose otherwise. Since I'm not familiar with their current production that might also make a search for a good classic part of the equation.
You also intimated that the sound, or lack thereof, was a critical factor. If so then you have already made one decision. A spring powered pistol will be the quietest of the 3 operating principles---spring, pnuematic or CO2. The P-1 that bearridge suggested is a very accurate gun with enough power to be deadly on snakes when used properly. But spring-piston airguns, pistols particularly, are the most difficult of the 3 to shoot accurately on a consistant basis.
You also imposed a limit of @ $100. You stated that you are or have been a serious pistol target shooter. I'm not at all certain that you can buy the accuracy you want at the price point you impose. It's the age-old question to new paper-punchers, "How much accuracy can you afford"? Because in that respect air pistols are no different from powder burners----the accurate barrels cost more.
If you don't mind elaborating on your expectations after reading my somewhat bleak word picture then we can take a better informed shot at a viable pistol that will meet your needs----tho the under $100 limitation may not be feasible.
As with firearms everything comes with trade-offs and I'm not deliberately being hard-nosed----just trying to present a realistic pic of some of the advantages and disadvantages inherent with the 3 types of powerplant and make a few observations that someone who likes accurate guns can relate to in a realistic fashion. Tom