What is a common technique for controlling buoyancy while diving?

Using an inflatable BCD (Buoyancy Control Device) to add or remove air is a fundamental technique for controlling buoyancy while diving. The BCD allows divers to adjust their buoyancy during the dive by inflating or deflating the bladder. When a diver adds air to the BCD, they become more buoyant and can ascend to shallower depths or float in the water. Conversely, removing air from the BCD makes the diver less buoyant, allowing for a controlled descent or staying at a certain depth. This manipulation of buoyancy is essential for effective diving, as it helps maintain safety and comfort underwater.

The other options do not provide the same level of direct control over buoyancy as the BCD. While weight belts can assist with initial descent by adding weight, they do not allow for the fine-tuning of buoyancy throughout the dive. Swapping tanks can adjust weight but is impractical in most situations. Swimming horizontally is a method for maintaining depth but does not address buoyancy control directly; it can often lead to increased air consumption and fatigue.