Emergency Ascent Procedures Every Diver Should Know

Why Emergency Ascents Are a Skill, Not a Rescue

The word 'emergency' in emergency ascent implies a failure — something went wrong. But in scuba diving, the skills associated with emergency ascents are taught precisely to transform potential catastrophes into inconveniences. A diver who knows what to do when they run low on air or find themselves without a buddy has options. A diver who panics does not.

Recreational certification courses cover emergency ascents in their practical skills requirements. These refreshers are useful beyond certification, because the skills degrade without practice.

Out-of-Air Emergencies

Running out of air is rare in well-planned recreational diving but it happens — equipment failure, distraction, buddy separation in poor visibility. The priority sequence:

1. Signal your buddy (out-of-air hand signal: hand cutting across throat repeatedly; or pulling their alternate air source directly to your mouth)
2. Use buddy's alternate air source (octopus): Your buddy holds the primary regulator; you use the alternate. Both of you ascend together at a controlled rate. This is the preferred response and why maintaining buddy contact matters.
3. Controlled emergency swimming ascent (CESA): If no buddy is available, you ascend under your own power, exhaling continuously to prevent lung overexpansion as ambient pressure drops. A CESA is viable from recreational depths (40m maximum) to the surface — air expands as you ascend, meaning there is breathable gas available throughout the ascent if you started with even a small amount.

The CESA rule: exhale continuously, especially in the last 9 metres where ambient pressure halves. A diver who holds their breath during a CESA risks an arterial gas embolism — a catastrophic and potentially fatal injury.

Buoyant Emergency Ascent

In an extreme out-of-air emergency with no buddy and no breath remaining, a diver can inflate their BCD fully and rise to the surface on positive buoyancy. This is the last resort — a buoyant ascent to depth allows the ascent to exceed the 9m/min safety limit and risks decompression sickness. The alternative is drowning. Do not confuse this with a controlled ascent.

The Safety Stop as Protocol, Not Option

For any dive deeper than 10 metres, a 3-minute safety stop at 5 metres is recommended. For dives to 30+ metres or multi-dive days, it is effectively mandatory. The stop allows additional off-gassing of dissolved nitrogen in the tissues and provides a buffer against micro-bubble formation.

In an emergency where you cannot complete a safety stop (loss of air, emergency at depth), surface immediately, report symptoms to your divemaster, and monitor for DCS signs for 24 hours.

Dealing with a Runaway Ascent

If your BCD or drysuit over-inflates and you begin ascending too fast:

1. Dump air from the BCD immediately via all dump valves
2. Dump air from the drysuit (drysuit divers) via the shoulder dump valve
3. Assume a head-up position and extend your arms slightly to create drag
4. If positively buoyant and ascending uncontrolled, exhale fully — this reduces buoyancy slightly and more importantly prevents lung overexpansion

A controlled ascent rate is 9 metres per minute or slower. Your dive computer will alarm if you exceed this. If you surface after a fast ascent, report it and monitor for DCS symptoms for 24 hours.

Buddy Separation Protocol

If you surface from a dive without your buddy and cannot see them, do not re-descend — you may miss them. The standard protocol: search the surface for 1 minute, then return to the boat and alert the divemaster. A search pattern will be initiated. Divers separated underwater are trained to spend one minute searching at depth, then ascend slowly to the surface.

Skip Breathing vs Controlled Breathing

Some divers attempt to extend their air supply by 'skip breathing' — taking a breath and holding it briefly between exhalations. This is not effective and is potentially dangerous: it increases CO₂ build-up, which causes an urgent breathing reflex at depth (hypercapnia), and reduces the diver's ability to respond calmly to a stressful situation. Efficient breathing technique — long, full breaths from the diaphragm — is more economical than skip breathing without the risks.