How does the depth of 66 feet relate to ATA in a dive context?

To understand how a depth of 66 feet relates to ATA, or Atmospheres Absolute, one must consider the pressure exerted by water at a given depth. The atmospheric pressure at sea level is 1 ATA, which is equal to approximately 14.7 psi. For every 33 feet of seawater, an additional ATA is added due to the water pressure.

At a depth of 33 feet, the total pressure is 2 ATA—1 ATA from the atmosphere and 1 ATA from the water above. Therefore, when a diver goes deeper to 66 feet, they are effectively at double that pressure. Thus, at 66 feet, the diver experiences an additional 2 ATA from the water – making the total pressure 3 ATA. This pressure calculation is crucial for understanding how it impacts gas absorption and narcosis during the dive.

Hence, a depth of 66 feet corresponds to 3 ATA total pressure, effectively influencing diving decisions such as gas management and safety practices.