Concept
Diving physics, or the physics of underwater diving is the basic aspects of physics which describe the effects of the underwater environment on the underwater diver and their equipment, and the effects of blending, compressing, and storing breathing gas mixtures, and supplying them for use at ambient pressure. These effects are mostly consequences of immersion in water, the hydrostatic pressure of depth and the effects of pressure and temperature on breathing gases. An understanding of the physics is useful when considering the physiological effects of diving, breathing gas planning and management, diver buoyancy control and trim, and the hazards and risks of diving. Changes in density of breathing gas affect the ability of the diver to breathe effectively, and variations in partial pressure of breathing gas constituents have profound effects on the health and ability to function underwater of the diver. The main laws of physics that describe the influence of the underwater diving environment on the diver and diving equipment include: Archimedes' principle (Buoyancy) - Ignoring the minor effect of surface tension, an object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. Thus, when in water, the weight of the volume of water displaced as compared to the weight of the diver's body and the diver's equipment, determine whether the diver floats or sinks. Buoyancy control, and being able to maintain neutral buoyancy in particular, is an important safety skill. The diver needs to understand buoyancy to effectively and safely operate drysuits, buoyancy compensators, diving weighting systems and lifting bags. The concept of pressure as force distributed over area, and the variation of pressure with immersed depth are central to the understanding of the physiology of diving, particularly the physiology of decompression and of barotrauma. The absolute pressure on a diver is the sum of the local atmospheric pressure and hydrostatic pressure.