Well over the years I have added rocks to my pockets on ocassion. I have a 5 pounder that is a bag of sinkers that I have collected off the bottom so the Stonz would work.
How about uranium, it would eliminate the lead issues, the glow stick enviromental disposal problems and would allow you to stay warmer in a thinner wetsuit?
With the market sinking David Doubilet had his Gold cast as dive weights so he could keep it close, unfortunetly he had to drop his weight belt in a down current and it hit and hurt his foot, that’s his story and he’s sticking to it!