MsDoe said: Any chance that he's a she, laying eggs? I think they come up on land for that.
My thought also. One year at our old house I watched a soft shelled turtle come out of the water and into the yard where she dug a hole at the base of a tree and laid her eggs before slowly moseying back into the water. I kept watch every day because I so wanted to see the babies but one morning I went out and something had dug up the eggs. Only one remained and it was broken open. I figured a raccoon or something got them.