Sorry to burst your bubble, but someone (possibly the guy who helped him up on that rock) went to the bank, hove a line to him, and either handlined him across or hauled his boat back to him. And he’s going to be hearing it about it in the pub for quite a long time.
No, I don’t know about this particular story, but that’s how these things usually end. It looked as if they had at least half a dozen guys on the river, no problem getting one of them across a little chute.