His grasp is easy to shirk given his lack of energy. It's simple enough to guess at what this stranger is trying to do - reckless as it is. Though thinning the ranks of the guards at the cost of this prisoner is nothing if not convenient, he himself would struggle to make it to shore. That would be wholly inconvenient.

"Then perhaps you can consider resuming your sightseeing when you have a better vantage point?" His emphasis on the words hints at another meaning to them. By all means, escape, distract the guards with a search. Just do it when he's not in the path of it.