Question

When a water bubble comes up from the depth of a pond , its volume is ?

Answer 1

Pressure increases with depth in water about 1 atm for every 10 m. The absolute pressure at the surface is 1 atm, so you'd need to go down about 30 m to get to an absolute pressure of 4 atm. If the temperature were pretty much constant, then you'd get your volume ratio of 4:1.