How much weight can 1 square foot of air pull to the surface from under water?

Question

How much weight can 1 square foot of air pull to the surface from under water?

Answer 1

1 CUBIC foot of fresh water weighs around 62.4 lbs.  If one cubic foot of air displaces 1 cubic foot of water, the buoyant force will be approximately 62.4 lbs.  (Neglecting the actual weight of one cubic foot of air)

1 SQUARE foot is a unit of area, not volume.  I have assumed you meant a volume measurement of 1 cubic foot.

Depending on the depth, the added complexity is that the 1 cubic foot of air will expand as it moves higher and the resulting pressure is reduced.

Answer 2

Roughly 62 pounds for a cubic foot at any depth, but the volume starts rapidly expanding as the balloon of air rises - if started at about 33 feet below the surface, by the time it reaches the surface it will have doubled in volume as the pressure goes from 2 atmospheres to 1.   Unless allowed for with expansion capacity or leakage, it will burst the balloon (as it does lungs in unfortunate divers) and it will rise faster and faster, which may cause the item lifted to bounce out of a sling or off a hook when the lifting force stops at the surface.