What technique can a diver use to manage buoyancy underwater?

The effective management of buoyancy underwater is crucial for divers to maintain an optimal and safe underwater experience, and using a buoyancy control device (BCD) is the primary technique for achieving this. A BCD allows divers to adjust their buoyancy by adding or releasing air from the device, which enables them to rise, descend, or maintain neutral buoyancy at various depths.

When a diver needs to ascend or descend, they can inflate or deflate the BCD accordingly. This tool not only facilitates comfort and control but also plays a significant role in preventing the risks associated with rapid ascents or descents, such as decompression sickness. The BCD is specifically designed for this purpose and is essential for any diver, thereby making it the most reliable method for managing buoyancy effectively underwater.

Other options, like holding the breath or descending rapidly, can lead to safety hazards. Holding breath while ascending, for instance, can cause lung expansion injuries, and descending quickly does not provide the control needed for safe buoyancy management. Diving without any equipment would not allow for proper buoyancy adjustment, as the diver would lack the necessary tools to regulate their position in the water.