Boyle's Law (pressure × volume)

Boyle’s Law states that as pressure increases, the volume of a gas decreases. This relationship is constant because the amount of gas stays the same while the environment squeezes it.

In diving, this affects everything from your buoyancy to your air consumption. When you descend to 20 m, the pressure is 3 times higher than at the surface. This means the air in your BCD or your lungs occupies only 1/3 of its original volume. You will feel this immediately as your buoyancy shifts during a descent.

Never hold your breath while ascending. If you ascend from 10 m to the surface without exhaling, the gas in your lungs expands by 2 times. This expansion can cause a lung overexpansion injury because the air has nowhere to go. Always breathe continuously to allow the expanding gas to escape safely.