Maybe it was possible he had a hunting camp nearby, and was getting some water from the river? Or maybe he was dropped off there by aliens.

A year ago at Ft Bragg I was going through special forces try-outs. I was doing land navigation and it was about 2 am and I strayed off course a good 3 clicks and I thought I heard someone following me. I stopped and bent over to rest my back and I looked up and there was this person staring at me 20 ft away, and I'm in the boonies near aswamp.I know it wasn't any instructors because I wasn't even on the course anymore. I thought maybe meth lab too. I thought I might have a fight to the death with this guy, but I acted like I didn't see him and turned and walked away.