What is the most common type of emergency ascent procedure?

The most common type of emergency ascent procedure is the controlled emergency swimming ascent (CESA). This method is favored because it allows a diver to maintain control over their ascent rate, which is crucial to avoid decompression sickness. During a CESA, a diver swims to the surface in a controlled manner, often exhaling continuously to prevent lung over-expansion as they ascend.

This approach is effective in ensuring that the diver can respond to changes in their environment and adjust their ascent speed accordingly. It is typically employed when the diver is at a depth where they can still swim effectively and when it is not possible to use other ascent methods such as deploying a buoy or using surface support.

In contrast, other ascent techniques such as rapid free ascent may expose the diver to a higher risk of decompression sickness due to the lack of control over the ascent rate. Surface ascent with delayed buoyancy control can be more complicated and is not as practical in emergency situations where immediate action is needed. Emergency powered ascent with equipment requires additional gear and is not suitable unless a diver is specifically trained and equipped for such a method. Hence, the CESA is the most appropriate and commonly taught emergency ascent procedure for divers in training and practice.