Sounds like a very effective solution, thanks
I don't think he knows something than nobody else knows, I don't think he's stupid either. He's just a young freediver learning his own ways. Soon there will be a new contraption in our garage similar to what Johnoly described, and my son will be curious about it and will decide to use it or pass on it. Whatever he chooses won't make him any brighter or stupider than any freediver in the planet.
Also for the record, I have seem other freedives towing their lines in that fashion.
I may agree with you not securing the line to myself, but it says nothing about the people that keep their lines secured to themselves. You and I are not bright and they are stupid.
Live and let live Dumpster. Your way, the champions way, or my way is not THE way. One size does not fit all.