In reply to IainRUK:
Once you are beyond neutral buoyancy, the amount of weight is kind of irrelevant. In sea water with a 2mm wetsuit, I wear 2kg. At 9m, I am neutrally buoyant. At 10m I will slowly start sinking. So I propel myself to around 15-17m then just stop, and my sink rate by then is equivalent to the speed I'd reached.
This is for my depths which are around 40m. My personal best is 45m.
With more weight, my neutral point would be shallower, so less effort needed on descent but more effort needed on ascent.
The much deeper divers will want to set their neutrally buoyant point much deeper, say 20-25m. Therefore they will tend to wear less weight and need to put more effort into the initial part of their descent.
I once had 4kg on by accident, didn't notice until AFTER a big dive (I had admittedly wondered why the ascent felt hard!). We did a quick test and found that I hadn't needed to bother with propelling myself at the start, because I was already sinking from the surface.
I am guessing that you dabble in a bit of spearfishing?
Post edited at 23:29