Just do what this chap did over the weekend, ignore the barrier ( there’s a small gap on the western end ) and park your motor boat in the safe area - just try not the run over too many kids and swimmers……..
I genuinely don't understand the attraction of the things. I've had a couple of goes on them when on holiday. After about 30 minutes one gets to feel, "OK, I've done that: gald I didn't buy one." A wetter and colder version of motorcycling I'd say. Actually, I much prefer bikes but I know if I buy another one, I will die. That's not a premonition as such; my wife would kill me.
Not a few serious swimmers on the Thames, tow a small but highly visible inflatable bouy attached to a belt. You can spot them some considerable distance away. Seems to not be an impediment regards swimming .