What does absolute pressure refer to?

Absolute pressure is defined as the total pressure exerted on a substance, including the atmospheric pressure and any additional pressure from a fluid above it. This concept is crucial in diving because as a diver descends, the pressure increases due to the water column above. Absolute pressure encompasses both the atmospheric pressure at the surface and the hydrostatic pressure due to the depth underwater.

This understanding is foundational for divers because it affects buoyancy, gas exchange, and dive planning. Knowing the total pressure helps divers calculate how gas behaves at various depths and how it impacts their diving safety and equipment. Other options, while related to pressure, do not encapsulate the comprehensive nature of absolute pressure, which is why the choice that describes it as the total pressure is the correct one.