Diving physics

These are the laws of physics that govern the physics of the SCUBA diver and of diving equipment:

Buoyancy - when in water, the density of the materials in the diver's body and in the diver's equipment determine whether the diver floats or sinks
Boyle's law - as pressure increases the volume of gases in the diver's body and equipment decreases
Dalton's law - in mixtures of breathing gases the concentration of the individual components of the gas mix is measured by partial pressure
Henry's law - as pressure increases the quantity of gas adsorbed by the tissues of the human body increases, increasing the risk of decompression sickness
Snell's law - the index of refraction of water is 30% greater than air and hence a diver cannot see clearly underwater without a diving mask with an internal airspace

Physical effects of water or the underwater environment:

Pressure - the overall pressure on a diver is the sum of the atmospheric pressure and the water pressure
Density - common materials found in body and in the diver's equipment such as air, water, steel and lead have widely differing densities.
Increase thermal conductivity in water, compared to air
Absorption of light and loss of colour underwater
Under pressure, gases compress but liquids do not
gravitational forces and the rotation of the earth cause tidal currents
Effects of weather such as wind, which causes waves, and temperature.