How common is running out of air?

Extremely rare among certified divers — under 1% of dives. When it does happen, the cause is almost always inattention to the SPG (pressure gauge), not equipment failure. Modern regulators are remarkably reliable; the human checking them is the variable.

The 4 emergency procedures, ranked

1. Alternate air source (octopus): signal your buddy 'out of air', take their octopus, breathe normally. Both ascend together. Preferred method.

2. CESA (Controlled Emergency Swimming Ascent): if no buddy nearby, exhale a continuous 'aaaah' sound while finning straight up. Works from depths up to 9m.

3. Buddy breathing: two divers share one regulator, alternating breaths. Falls behind octopus method but useful if buddy's octopus fails too.

4. Buoyant emergency ascent: drop your weight belt, exhale continuously, ride buoyancy to the surface. Last resort — risks rapid ascent injuries.

Hand signals you must know

'Out of air': flat hand sliced horizontally across throat. 'Share air': two fingers pointed to mouth. 'Going up': thumbs up. 'Low on air': closed fist tapped on chest. Practise these on every dive — in an emergency you have no time to remember them.

How to prevent out-of-air situations

Check SPG every few minutes — not 'occasionally'. Plan turns at 100 bar on a single tank, exit water at 50 bar. Rule of thirds: 1/3 out, 1/3 back, 1/3 reserve. Stay with your buddy within reach. Don't push depth or time beyond your computer's limits. Service regulators annually.

After an air emergency

At the surface, signal the boat, inflate BCD, drop weights if needed. Don't dive again that day — you've been through a stress event. Brief your dive operator on what happened so they can review with you. Log it in your dive log honestly — future buddies need to know about close calls.