Learned from a professional freediver that most people-I used to be one-use too much weight and that causes to spend a lot of energy trying to stay afloat.
That means about 3 - 6 lbs for an average person.
I learned that you should be neutrally buoyant at 30 feet, anything deeper than that you should be freefalling. Also you need to wear the belt low around your hips, human ribs and lungs are semi flexible and you don't want to restrict the expansion of these organs during ventilation cycle.
