A scuba diver experiences increasing pressure as they descend deeper. Approximately how much does pressure increase per 33 feet (10 meters) of depth in water?

Pressure in a fluid increases with depth at a predictable rate. P = ρgh, where ρ is fluid density, g is gravity, h is depth. For water: ρ = 1000 kg/m³, g = 9.8 m/s². Pressure increase per meter of depth = 1000 × 9.8 = 9800 Pa per meter ≈ 9.8 kPa/m ≈ 1.4 psi/m. So 33 feet (10 meters) ≈ 14 psi pressure increase, or about 1 atmosphere (atm ≈ 14.7 psi at sea level). Total pressure at depth = atmospheric pressure (at surface) + water pressure (due to depth). At 33 feet depth: total pressure ≈ 2 atm (1 atm air + 1 atm water). At 66 feet: 3 atm. At 99 feet: 4 atm. This affects scuba diving in important ways: (1) GAS COMPRESSION — at 33 feet, lungs and gas spaces compress to half their surface volume per Boyle's Law; at 99 feet, to one-fourth; (2) BREATHING — divers need pressurized gas equal to surrounding water pressure to inflate lungs; modern regulators automatically adjust; (3) NITROGEN ABSORPTION — at higher pressure, more nitrogen dissolves in tissues (Henry's Law); ascending too fast releases nitrogen as bubbles (decompression sickness, 'the bends'); divers ascend slowly with decompression stops on deep dives; (4) OXYGEN TOXICITY — at high pressure, even normal-percentage oxygen becomes toxic (~6 atm); deep divers use special gas mixtures; (5) NITROGEN NARCOSIS — at depth, nitrogen affects the central nervous system; called 'rapture of the deep'; reversible upon ascent. Salt water is slightly denser than fresh water, so pressure increases slightly faster (about 33 feet per atm in salt water, 34 feet per atm in fresh). Atmospheric pressure at sea level: 1 atm = 14.7 psi = 101 kPa. Decreases with altitude (about 0.3 psi per 1000 ft elevation).