You may have noticed during Open Water training with RAID that we do not emphasize or promote CESA (Controlled-Ascent Emergency Swimming Ascent). The simple reason is that executing a CESA is inherently hazardous, and relying on it as anything but a last resort is foolish. In an actual out-of-air emergency, there are much better options… and those we teach.
But first, let’s look at what’s wrong with the mindset that suggests CESA works.
The issue is a basic human failing: the Psychological and Physiological Panic Loop.
An out-of-air emergency triggers an immediate adrenaline surge. This triggers a natural but undesirable human instinct: suddenly deprived of air, a common reaction is to hold one’s breath and kick frantically upward.
Fighting this hardwired survival reflex requires immense discipline. Most fail to manage that panic; the CESA devolves into an uncoordinated scramble that breaks every rule of safe diving protocol.
Too often, the outcome is a dismal failure: pulmonary barotrauma occurs, leading to arterial gas embolism (AGE), pneumothorax, or mediastinal emphysema—any of which can be rapidly fatal or cause catastrophic neurological injury.
Since its beginning, RAID instructors have taught ‘Modern Alternatives’ to CESA. These put a heavy emphasis on buddy awareness and redundancy—such as carrying an independent gas source, having a redundant second stage on a long hose, and meticulous gas management protocols (like rule of thirds and minimum gas calculations).
RAID also suggests divers practice buddy-assisted OOA simulations regularly. For example, at the end of a normal dive as a ‘protocol and skills practice ‘. A good ending for a perfect dive is to occasionally practice a controlled gas-sharing ascent with your buddy to your regular five-metre safety stop. (N.B. NOT A CESA.)
A CESA remains the absolute last resort for catastrophic failure when all other options—particularly careful gas management and diving with a reliable buddy—have been ignored. Most importantly, it is not an acceptable primary contingency for poor dive prep. Although CESA is a required part of every agency’s curriculum for new divers, it is taught as a last-ditch survival skill for out-of-air situations; treating it as a reliable or casual fallback plan carries severe physiological and operational risks.