What action can increase buoyancy while diving?

Inflating a buoyancy control vest is the correct response as it directly increases buoyancy by adding air to the vest. The vest creates additional positive buoyancy, counteracting the weight of the diver and any gear, which allows the diver to ascend or maintain a neutral buoyancy level in the water.

When air is added to the vest, it decreases the overall density of the diver. This principle follows Archimedes' principle, which states that an object will float if the buoyant force is greater than its weight. By inflating the vest, the diver effectively increases the volume of displaced water, leading to greater buoyant force.

The other actions mentioned do not serve to increase buoyancy. Descending quickly typically results in increased pressure and can lead to complications rather than buoyancy changes. Using heavier weights increases the overall weight of the diver, effectively decreasing buoyancy and making it harder to float. Finally, removing air from the lungs increases the density of the diver, which also reduces buoyancy.