Of course, every thick brown snake spotted by visitors in the Okefenokee is a venomous Cottonmouth, or Water Moccasin (note the sarcasm!). I must admit, the Water Snakes (Genus Nerodia) do bear more similarities to the Cottonmouth than most snake species. The Water Snakes, like Cottonmouths, are a dark color, have thick bodies and roughly keeled scales. I can understand how those with just casual experience with snakes might be confused. So I cut them a break and try not to act too offended!
The US Fish and Wildlife Service lists four species of Water Snake within the refuge. Although they are not venomous, I wouldn’t call them totally “harmless.” They can really put up a good fight of striking, hissing and musking… but this only happens to the people that try to grab them! If you keep your distance, they generally lie perfectly still or make and escape.
The majority of the time, the only thing visitors see of the Okefenokee’s water snakes is a splash into the water as the snake drops from an overhanging branch, usually before your canoe is within 100 feet of them. So it is often difficult to know which species you may have encountered.
iNaturalist observation: https://www.inaturalist.org/observations/29977758