A diver weighing 175 lbs is neutrally buoyant in saltwater. How must they adjust their weight to achieve neutral buoyancy in freshwater?

To achieve neutral buoyancy in freshwater, the diver must remove weight. The principle behind this adjustment lies in the differences in density between saltwater and freshwater. Saltwater is denser due to the dissolved salts, providing more buoyant force compared to freshwater. When the diver is neutrally buoyant in saltwater, they are balanced perfectly between the upward buoyant force and their weight.

Since freshwater is less dense than saltwater, when the diver enters freshwater with the same weight, they will experience less buoyant force. This can lead to the diver becoming negatively buoyant, meaning they would sink. To adjust for this, the diver needs to remove some weight so that their overall weight matches the reduced buoyant force in freshwater, allowing for neutral buoyancy again. This understanding of buoyancy and density differences is crucial for divers to maintain control and safety while underwater.