quite a few other powerboat qualified people on here, I see.
If the kill cord was indeed in the bottom of the boat (as someone mentioned) then what happened is what I thought when I first saw this. Driver was going too fast, doing doughnuts, The boat tips to one side, he falls over the edge and as he does, wrenches the wheel to full lock one side. Hence the boat starts going in circles with spinning knifeblades at the back. The panicking crew are also thrown out into the middle of the circle and...don't think any further.
how do I know? Because this is a classic 'what not to do' and is taught on even the most basic powerboat course. You are also taught to keep the engine away from anyone in the water, and as soon as they touch the boat, you stop the engine. Or earlier and let them swim or drift to you.
of course, if the kill cord had been attached to his leg then the engine would have stopped as he went over the side. So his stupid manoeuvres would only have ended in him getting wet.
I've never been on a jetski (horrendous noisy things) but I believe that they have a dead man's handle and automatically stop if you let go.
sailing dinghies don't need qualifications - but you don't get far with no knowledge, you capsize almost immediately. So it is self-limiting.
The RYA campaign for sailing and powerboating qualifications NOT to be compulsory - but to be recommended and accessible to all. The courses cost peanuts and there is no excuse for anyone who can buy a powerful RIB not to take one.