In terms of pressure, which unit is equivalent to 33 feet of saltwater?

The pressure exerted by a column of water depends on the density of the water and the height of the column. In saltwater, the density is approximately 64 pounds per cubic foot. As a rule of thumb, every 33 feet of saltwater exerts an additional pressure of about 14.7 psi due to the weight of the water above that depth. This value is significant because it closely approximates the atmospheric pressure at sea level, which is also 14.7 psi.

Thus, at a depth of 33 feet in saltwater, the pressure experienced is effectively the addition of the atmospheric pressure (14.7 psi) plus the pressure from the water column, making it critical for dive planning and understanding dive tables, as the total pressure on a diver increases with depth. This application of pressure units and their relationship to depth is essential for safe diving operations, ensuring divers are aware of the pressures they will encounter.

The other options do not align with this key relationship between depth in saltwater and pressure.