Did you know there’s an almost mile-long cave system under the Withlacoochee River between Lowndes and Brooks Counties, Georgia? Valdosta cave-diver Guy Bryant wrote a fascinating in-depth blog about McIntyre Spring, including this map he drew, and the picture below of him in this cave system that starts in the river bottom.
There’s no land access, so don’t trespass. And don’t try to go in the cave even from boats unless you really know what you’re doing. It’s been visited by some of the most famous cave divers in the world, a couple of whom are no longer with us due to accidents in other underground caverns.