How to Perform a Controlled Emergency Ascent
Learn how to perform a controlled emergency ascent while scuba diving — a life-saving skill every diver should practice and understand.
SAFETY WHILE DIVING
How to Perform a Controlled Emergency Ascent
No one plans to run out of air underwater. But it can happen. A forgotten SPG check, a malfunction, or just poor air management — suddenly you're low at depth, and you need to ascend safely. That’s where a Controlled Emergency Swimming Ascent (CESA) comes in.
This technique is used when you’re out of air and your buddy isn’t within reach to share theirs. It's not ideal — but if you do it correctly, it can get you to the surface without serious harm. The key word is controlled — panic is your worst enemy here.
Start by dropping any unnecessary weights (unless you’re wearing a weight-integrated BCD you can adjust). Look up, raise your arm to protect your head, and kick steadily toward the surface. Exhale slowly the entire time — never hold your breath. Let out a continuous stream of bubbles to reduce the risk of lung overexpansion.
It helps to make a soft “ahhh” or humming sound as you exhale — it’s a good reminder to keep air moving and stay calm. You’re not racing to the surface; you're just moving with purpose and control. If you’re deep, aim for no faster than 30 feet per minute.
If you’re diving with a dive computer (Check out the Shearwater Peregrine TX dive computer I use on Amazon), it may warn you of a fast ascent — that’s okay in an emergency, but always try to stay within safe limits if you can. Once you reach the surface, inflate your BCD immediately and signal for help if needed.
This isn’t just something to read about — it’s a skill that needs practice. Many open water courses include a CESA from shallow depths, but you should refresh this skill during checkouts or pool sessions. Practice builds muscle memory and reduces panic if the real thing ever happens.
Of course, the best emergency ascent is the one you never need to make. Monitor your air. Stay close to your buddy. Know your limits. But if things ever go sideways, knowing how to ascend with control could make all the difference.
Happy and safe diving,
The ScubaBlast Team
PADI. (n.d.). Controlled Emergency Swimming Ascent (CESA). Retrieved August 6, 2025, from https://www.padi.com/articles/controlled-emergency-swimming-ascent-cesa
Divers Alert Network. (2023). How to Handle an Out-of-Air Emergency. Retrieved August 6, 2025, from https://dan.org/health-medicine/health-resource/dive-emergencies/out-of-air-scenarios/
Scuba Diving Magazine. (2022). Emergency Ascent Tips. Retrieved August 6, 2025, from https://www.scubadiving.com/how-to-perform-emergency-ascent