I’m also a bit heavy and I know the struggle. I use a lot of energy just do prevent popping back up like a cork. I’ve considered using a little bit of lead, but what I like about freediving is not having a bunch of belts and vests and other gear on me. So I’m currently also trying to lose weight.
You can go much deeper than 10 fathoms without supplemental oxygen, half the people reading this right now could do it with some training.
The world record is 117 fathoms on a single breath.