Diving safety

In short

Diving safety relies on clear organisation (who decides, who you dive with), checks before every dive, good air management, hand signals everyone knows and a few reflexes for the unexpected. Above all, it starts with a simple decision: only dive when you feel well, in conditions suited to your level. This guide gives the essentials; procedures are learned and practised with an instructor.

Why it matters

Most diving incidents do not have a single cause but come from a chain of small problems: a leaking mask, a bit of stress, a buddy lost from sight, higher air consumption than expected. Each safety rule is there to break this chain as early as possible. When you are well prepared, a small problem stays small.

Organising the dive

Roles

• The dive supervisor is responsible for the organisation on site: they choose the site according to the conditions, form the dive teams, set the parameters (maximum depth and time) and organise emergency response. In France, this role is defined by the French Sports Code.
• The dive leader guides the supervised divers, chooses the route underwater and keeps an eye on everyone.
• The dive team (palanquée) is the group that dives together; when diving autonomously, each diver looks after the others. Your buddy is the diver you watch first and who watches you.

Briefing and debriefing

The briefing, before the dive, presents the site, the conditions, the parameters, the route, the safety instructions and the signals. Listen to all of it and ask your questions. The debriefing, after the dive, is for sharing what went well and what can be improved: it is a time to learn, not to blame.

Before the dive: checks

• Your equipment: cylinder open and pressure checked, regulator and octopus (alternate air source) breathing correctly, BCD inflator inflating and dumps working, weights secured, mask, fins, dive computer on.
• The buddy check: each diver checks the other's equipment (see the water entry guide).
• Announced parameters: maximum depth, maximum time, turn-around and reserve pressure. Repeat them to your buddy.

Managing your air

Air is your vital resource. Check your pressure gauge regularly, much more often than you think at first.

• The reserve is an amount of air you never use during the exploration: it is for the ascent, the stop and the unexpected. Its value is set at the briefing (often 50 bar).
• The rule of thirds, used on some dives (current, wrecks, out-and-back routes): one third of the air to go, one third to come back, one third in reserve.
• Report your pressure when the guide asks, and signal half pressure and reserve without waiting.
• Cold, stress, exertion and depth increase air consumption.

Communicating underwater

The basic signals are shared by most organisations, with some variations: have them confirmed at the briefing.

Signal	Meaning
Thumb and index finger in a circle, other fingers extended	OK, all good (question or answer)
Flat hand, rocking	Something is wrong
Thumb up	Go up (it does not mean "OK" underwater)
Thumb down	Go down
Closed fist at shoulder height	Reserve reached
Hand slicing across the throat	Out of air
Open hand beating in front of the chest	Out of breath
Arms crossed, rubbing the arms	I am cold

At the surface, an arm forming a circle above the head means "OK"; an extended arm waved up and down is a call for help.

Losing your team

If you can no longer see your group: turn slowly on the spot, looking around, above and below, for about one minute. If you cannot find them, ascend slowly, respecting the ascent rate and the safety stop, then wait at the surface and make yourself visible. The team follows the same procedure: everyone meets at the surface. The dive supervisor specifies this procedure.

Emergencies

• Out of air: signal your guide or buddy, who gives you their octopus (alternate second stage). Breathe calmly, hold on to each other and ascend together. These skills are practised in training.
• Breathlessness: stop all effort, hold on to something if possible, breathe out fully and slowly, tell your guide. It gets worse if you keep finning: ascend calmly if it does not pass.
• Cold: it tires you, increases air consumption and favours decompression sickness. Signal it early; the dive is cut short.
• Narcosis (nitrogen narcosis): beyond about 30 m, nitrogen can cause euphoria, anxiety or difficulty thinking. It disappears when you ascend a few metres.
• Emergency ascent: as a last resort, with no air available, ascend breathing out continuously so as not to trap air in your lungs (see the barotrauma guide).

Being seen at the surface

A surface marker buoy (delayed SMB) inflated from the safety stop shows your position to the boat. A whistle, and possibly a torch or a mirror, completes your signalling kit. At the surface, inflate your BCD and stay together.

Helping others

• Get trained: the RIFAP qualification in France (response and intervention in a diving accident) teaches you to get a casualty out of the water, monitor vital functions, give oxygen and call for help.
• Calling for help: at sea in France, the CROSS on VHF channel 16 (preferred on board) or 196, free, 24/7; on land and throughout the European Union, 112. These numbers are valid as of the guide's update date; abroad, ask at the briefing.
• Oxygen: oxygen administration is the key action while waiting for help, performed by a trained person.
• Evacuation form: the dive supervisor fills in a document that goes with the casualty (identity, dive details, time of signs, actions taken).
• DAN (Divers Alert Network) offers specialised diving medical assistance and insurance.

Personal factors

• Fitness: fatigue, lack of sleep, stress or illness (especially a cold) are good reasons not to dive.
• Medication, alcohol, drugs: they affect alertness and reactions. Ask a doctor for advice about any treatment.
• Hydration and food: drink water, avoid diving on an empty stomach or after a heavy meal.
• Calling a dive: cancelling a dive or ending it early is a decision made by experienced divers, never a failure. Anyone can stop at any time, without having to justify it.

Key takeaways

• Listen to the briefing and respect the dive supervisor's parameters.
• Check your equipment, then your buddy's, before every dive.
• Watch your air and respect the reserve.
• Stay with your team; if you lose it, everyone meets at the surface.
• In an accident: oxygen, call for help (VHF 16, 196 or 112), never back into the water.
• Only dive when you feel well: calling a dive is part of safety.

Further reading

While recording, the watch shows your depth, dive time and stops, and alerts you if you ascend too fast. Key events (alerts, safety stop) are kept in the session's event log, which you can review later in your logbook. These alerts complement your training and your dive computer; they do not replace them.