Unfortunately this is a problem that we grapple with every year in the off season. The best we can do is try to get the number on the jet ski and report it to Harbor Patrol. We’ve been told that we should call 911 if they are putting people’s lives in danger. We have a resources page on our site with numbers to call.
The caveat is – we are not permitted to swim without lifeguards so anyone that does is also breaking the law.
I find it best to swim early morning. Later in the afternoon it gets dicey with boats and jet skis. And never head out alone – wear a bright cap and buoy.