What is a Controlled Emergency Swimming Ascent (CESA) and how do you safely execute one?

It’s a mantra in diving — “plan the dive and dive the plan.”

However, sometimes, usually due to diver error, a Controlled Emergency Swimming Ascent (CESA) may be your only option.

A 2009 DAN analysis of diving accidents reported on 964 total diving fatalities. Within that study, 288 instances involved emergency ascents that had gone wrong. The most common triggering factor in the decision to abort a dive and make an emergency ascent was running out of breathing gas. Now, if the diver had dived the plan in conjunction with his buddy and recommended dive procedures, these incidents likely wouldn’t have happened at all. But, if the emergency ascent was necessary and conducted correctly, the diver would have stood a much greater chance of survival and, at a minimum, mitigated any injuries.

Instructors teach emergency ascents within the basic training curriculum for the PADI Open Water course. Students learn the CESA in confined water first, and then the instructor assesses them in an open-water environment on either qualifying dive two, three or four. Then, sadly, most divers never practice a CESA again.

What is a CESA?

Ideally, if you’ve planned and conducted a recreational dive correctly, the dive should end with a normal ascent. Divers should recognize their turn point for gas and/or no-stop time. They should ascend as a buddy pair at a safe ascent rate to 15 feet (5 m), complete their safety stop, and return to the surface together. Once there, they should establish positive buoyancy with a pre-agreed reserve of gas.

For whatever reason, one buddy might have a low-on-air/out-of-air situation at depth. For this circumstance, open-water courses cover an alternate-air-source assisted ascent. One buddy acts as the air donor and the other as the receiver. Then, in close contact, they make their way to the surface at a safe ascent rate. As they break the waterline, the out-of-air diver achieves positive buoyancy by orally inflating his BCD or dropping his weights. His buddy, the donor, supports him.

The CESA comes into play for a third scenario: if you find yourself alone in a low-on-air/out-of-air situation in 20 to 30 feet (6 to 9 m) of water or less. You may also be closer to the surface if you’re at that depth than you are to your buddy to share air.

Note that both the first and second ascent scenarios outlined above rely on your buddy being close by — and they should be. After all, within the open-water qualifying dives one of the requirements is to “stay close enough to make physical contact with your buddy within two seconds.” However, as we gather experience, however, divers often drift away from their buddies. This can be due to a sense of security or good visibility, distracting technology underwater or marine life. Buddies may simply become separated due to poor visibility, navigation or poor buddy communication. In any case, your buddy may not be where you expect him to be. Thusly, having well-practiced CESA skills is critical.

How to safely conduct a CESA

Picture it: you’re happily swimming around a shallow tropical reef with your buddy at 30 feet (9 m). When you check your gas supply, you’re nearly at the agreed ascent pressure. Then, you spot a tiny ghost pipefish camouflaged in a tuft of coral. You pause and hover next to the reef, watching as the pipefish drifts in the gentle surge. You decide to take a photo to show your buddy on the boat later. As the water moves you backward and forward and you adjust the white balance on your camera, you struggle to get the shot you want for a few minutes. Five, 10, 20 shots and then, finally, you get your dream shot. Happy now, you look up to find that your buddy didn’t stop when you did. And, what’s worse…you’re out of air. This is a CESA situation. Now what?

  1. Don’t panic. Stop, think, act. Remember your training.
  2. Signal out-of-air with the universal “slashed-throat” sign. Your buddy may not be close, but on a resort reef there may be another diver outside of your immediate field of vision who can assist with an alternate-air source.
  3. Look up. This will help you to judge the distance to the surface. Most importantly, this will ensure your airway remains open so that any expanding gas can escape. Remember: at a depth of 30 feet (9 m), any residual gas in the lungs will try to expand to 1.9 times the volume on the way to the surface.
  4. Lift your low-pressure inflator with your left arm and poise your finger over the deflate button. Any residual gas in your BCD will also be trying to expand to 1.9x the volume on the way up. If you don’t vent it in a controlled manner, you will have a rapid ascent. This can lead to potentially more serious problems.
  5. Raise your right arm above your head, which will protect you from anything you can’t see above you as you begin your ascent.
  6. Begin kicking toward the surface and, as you do so, exhale gently so that expanding gas exits the lungs. In training, divers usually learn to make a continuous “ahhh” sound.
  7. During your ascent keep the regulator in your mouth. If you instinctively attempt to take a breath, it’s better to breathe against an empty regulator than inhale a lung full of salt water. Any residual gas in the hoses will expand on the journey to the surface, so you may get a small amount of air.
  8. Maintain a normal ascent rate. PADI states a 60-foot (18 m) per minute maximum ascent rate. This means surfacing from 30 feet (9 m) should take approximately 30 seconds. If you have a wrist-mounted dive computer, start wearing it on your right wrist. This way you can release gas from an extended BCD/Wing LPI hose if necessary while simultaneously monitoring your ascent rate on your computer.
  9. Keep kicking. As you breach the surface, you’ll need to obtain positive buoyancy. Both your BCD and your cylinder will be nearly empty. Orally inflate your BC while you continue kicking. Use either a continuous barrage of kicks or the bobbing method. If you’re struggling to orally inflate your BCD release your weights.

Once you’re positively buoyant at the surface, hopefully your buddy — having searched for one minute and then abort to regroup at the surface — will be there to help you back to the boat or shore.

The CESA is an important emergency-ascent skill and certainly one worth practicing. However, do not practice this in open water going directly to the surface from depth. As with all scuba skills, if you haven’t practiced for a while, do so with a professional in a pool or confined-water environment. If you want to practice a CESA, conduct it horizontally over a 30-foot (9 m) distance to simulate the process. Or, if space allows, swim diagonally over that same distance to the surface from 10 feet (2 to 3 m) at the bottom of the pool or shallow, confined-water environment.

Divers often overlook the CESA after initial training, but comfortably and competently performing the skill in an emergency is crucial. Don’t let a bad diving day turn into something much worse.

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