I was hiking out in the woods along the lake the other day, and hadn't seen another soul the entire way out there. I was sitting on a rock by the shore, listening to the haunting cry of a barred owl. (I only figured out later it was a barred owl as I recorded his call and found it later online:
http://www.allaboutbirds.org/guide/barred_owl/sounds.)
As I sat there, contemplating the universe, some THING appeared in the water. At first I thought it was a huge turtle, with its big funky head plowing through the water and a hint of a hump behind. Then I realized it wasn't a turtle because it did this sinuous flip and dove. The rational part of my brain was like - well, erm, OK, it's just some...thing... The part of my brain saturated in Supernatural was freaking out a bit, thinking: I'm sitting miles from anywhere, completely alone, on the edge of a lake, with my feet dangling inches above the surface, and some THING is 5 yards away from me, gliding through the water and then diving... Should I run?
I admit to pulling my feet up.
It didn't reappear - that thing could hold it's breath, I'm telling you, because I walked along the shore looking for it and didn't see it again.
Current hypothesis: a nutria - these weird beaver-like critters with long skinny tails.