What defines one atmosphere of pressure?

One atmosphere of pressure is commonly defined as the pressure exerted by the weight of the atmosphere at sea level, which is equivalent to 1 ATA (atmosphere absolute). In terms of water pressure, every 33 feet of seawater contributes to an additional atmosphere of pressure, due to the density of saltwater being greater than that of freshwater. Since freshwater has a different density, it takes about 34 feet to reach one atmosphere of pressure.

When considering all of these measurements, they collectively help define what it means to experience one atmosphere of pressure, whether experiencing this at the surface or underwater across various water types (fresh or salt). Therefore, saying that all these measurements contribute to our understanding of atmospheric pressure is entirely accurate and reflects the principles of underwater pressure dynamics. This interconnectedness makes the comprehensive understanding of atmospheric pressure in both marine and aquatic environments essential for divers.