This turtle has become the watchdog of the pond. He perches himself upon one of the rocks and if he sees something he doesn't like he disappears into the water very quickly which warns other inhabitants in an alarm fashion. I must admit that I have never looked it up but turtles must have the eyes of a hawk. My deck is at least 75 yards away and he use to sink into the water as soon as I would step out. I think he knows me now and pays no attention. By the way he stayed in this position for a long long time. The dark spot on its back appears to be his shell torn up or peeled up like an injury.