Well, he could always wear a condom while swimming......
That won’t work. A finger cot might stay on.
It’s funny that you said that. As a matter of fact, there is a very miniature creature in the waters in New Guinea highlands, that just does that. It enters the urinal tract of a human being, and settles in the bladder to lay it’s eggs. It’s very painful to get rid of it, That’s why, when crossing a stream, you must plug every orifices in your body. I chose a condom for the front and a plug for the rear end.