Density & Volume: Effect of Pressure on Buoyancy

[6MDM]

If a one cubic foot balloon is reduced to half the volume at 2atm or 33ft of water and is two times as dense, Is water at that depth also two times as dense making bouyancy constant at 2atm or even deeper?

 

[phyzguy]

No, water is relatively incompressible, so its density at 2 atm is only slightly higher than at 1 atm. So the buoyancy of something containing air (like a baloon) is reduced as it is submerged deeper. If you've ever scuba-dived, you would know that the buoyancy of your body is reduced as you dive deeper, because your lungs contain air and so you act like a balloon of sorts. This is why you wear a buoyancy compensator to which you add air as you go deeper to maintain yourself in a state of neutral buoyancy.