Yeah, no kidding, those damn turtles just pop up and can really get the adrelaine going.  We had a daily visitor on Crooked at one camp, was huge, netted him once to inspect.  Pulled up on shore,  shell was more than 3' across, measured with string across longest part.  Slimy, leech or parasites sucking on skin parts on legs, wild stab on weight, we lifted it up, 50#.  Then it got mad, started hissing.  Needless to say we were very careful not to be anywhere near the head anytime!  Manoevered by holding tail.  What a beast.