He saw a naked girl, stared at said naked girl, realized that he shouldn't see [I]or[/I] stare at naked girls and, in an act of desperation, made a clumsy attempt to escape (whether he meant simply to stand up and run away, perform an impressive acrobatic maneuver before making his exit or simply kicked out his legs randomly with no plan of action in mind is up for debate) and ended up lying face-down in the mud behind the log he was sitting on.

Quite simple, really. He's... a bit odd like that.