This item states that it can lift 20 lbs into the air by filling a 3' diameter balloon with a lighter than air substance as a move action. So I am thinking that I want to tie this to my character and crack it open to bring me to the surface when I can't make a swim check.
To figure out what is the net weight of a person in water I did some research online for this specific question and I did some math with average volume and weight and think that the percentage a person weighs in water in terms of net force is in the ballpark of 11% and 12% of what they weigh out of the water. This would mean the same 20 lbs balloon could lift about an 180 lbs person even it didn't blow up to 3ft in diameter. Once you figure in this extra volume of the balloon, the weight it could carry would go up dramatically.
So my questions is, can I use the buoyant balloon to surface in the water automatically? Physics seems to say yes.