Dr. Lecter
Contributor
Of course the public elected it, I didn't forget it. What are the alternatives? Let the diver rot in there? Wait until the relatives pay for the recovery? (I'm assuming the diver is dead - since nobody paid for the helicopter/car/rescuer's equipment/training) Wait until the volunteers pull him/her out? Place a sign "if you find a dead diver, please call this number"?
Those are all equally-valid options in terms of your prior argument that because the public bore the cost of screwups, it had some kind of moral right to control the activity. If you didn't forget nobody forced the public to bear that cost, then you were simply being disingenuous by claiming that because they had to do something they received a concomitant moral authority to regulate to reduce costs it had to bear.
And we must be talking about moral obligations and authority, because there's zero question that a state or locality has the legal authority to do whatever it wants with SCUBA diving (at least in the US). The general police powers entrusted to such governments allow them to set whatever regulations on the activity they want--regardless of whether they're paying for cleanups on aisle 130'--or simply ban it outright.