My thoughts are that it would be great until your insurance company found out about it. You increased your (their) liability factor exponentially. I don’t know how the "my client drowned because this irresponsible and reckless instructor tied him up with a net/rope" thing would play out in court. I suspect even a half-butt attorney could take that all the way to the bank.
(not suggesting your idea is irresponsible or reckless. We all know how lawyers put the spin on things)