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Rescue procedures for Freediver Blackout

One of the greatest risks in freediving is freediver blackout – no matter if it occurs in shallow water, deeper water or from what is called CO2 blackout. This diving malady is probably the biggest argument for diving with a buddy, who can support and assist you in the event that you should succumb to blacking out. Unfortunately, this is the type of emergency that cannot be recovered from without the assistance of your dive buddy or other surface support. When one blacks out, they become unresponsive. In cases of Shallow Water Blackout (SWB), the freediver swimming towards the surface will exhibit various symptoms that will be readily apparent to the trained eye.

Signs and Symptoms of Freediver Blackout

Although there are many different signs/symptoms of blackout, a dive buddy or surface support person who isn’t experienced with this diving malady may not recognize its occurance immediately. For the diver who is ascending, by the time the symptoms begin to occur for blackout, it is usually too late and the diver looses consciousness soon after. For the dive buddy or surface support personell, careful observation for the beginning symptoms or signs is paramount to a successful rescue. They are as follows:

  • The diver stops swimming for no apparent reason
  • The divers legs become slack
  • The divers arms may fall down to the sides of their body
  • The divers eyes may roll back or close as they become unconscious
  • Their head may roll forward or drop down onto their chest
  • The diver will begin sinking
  • A convulsive twitching or spasming may occur

A diver who has succumbed to blackout, will upon reaching the surface, regain consciousness within moments of having been assisted to the surface. However, while the diver is still unconscious underwater, they have now become a potential drowning victim. While the unconscious diver is sinking, they have lost most of their voluntary bodily control. But they still have protective reflexes that help to assist in the rescue process. One of those reflexes is called the laryngospasm. A laryngospasm closes off the vocal cords, thus preventing water from entering the respiratory system. A laryngospasm, after time, will relax which at that point will cause problems if the freediver is still submerged underwater. More than likely, when the diver has reached the surface, and by keeping the divers head out of the water, the laryngospasm will cease and breathing will resume by the freediver who had blacked out.

After a period of time if the unconscious freediver has not been assisted to the surface, the laryngospasm will eventually relax and water will enter the lungs which will cause problems after resuscitation is successful. Immediate resuscitation of the diver may be hindered at first by the laryngospasm, which will block any air entering, but it will eventually relax and in-water resuscitation can then begin. If water has indeed entered the lungs, careful consideration must be given with the now near-drowning diver. Even if they appear fine after successful resuscitation, they may still suffer from what is called a socondary drowning for up to 24 hours after in the incident due to water residing in the respiratory system. It is strongly advised that the rescued diver who has undergone the near-drowning event seek immediate medical treatment /evaluation – even if they say the feel better.

The dive buddy should always be well ventilated, or in other words, should not be out of breath while at the surface observing their submerged dive partner. This is so they can ready should they need to respond to this type of dive emergency. Once the dive partner at the surface recognizes that their buddy is in crisis, clear thought needs to be given to the appropriate response. Several deep breath cycles or ventilation’s should be taken to assist the rescuing diver in the rescue of the unconscious diver. The following techniques are used in the rescue process.

Assisting the Unconscious Diver

Care should be given when assisting the unconscious diver to the surface who has experienced blackout. This physiological response is the body’s voluntary response to the impending physical condition of critical hypoxia. The rescue person should take care in not startling or aggravating the unconscious divers body, such as slapping or yelling at them, as this could cause them to stay in an unconscious state.

The following care should be given to the unconscious diver:

  • The divers head should be supported by cradling their neck
  • To help prevent the diver from taking in more water, cover the divers mask and mouth with your free hand (the one not cradlng their neck)
  • While maintaining firm contact with the unconscious diver, swim to the surface, supporting them all the way to the surface
  • once at the surface, tilt the head upwards slightly to keep the airway open
  • Any flotation device, such as a surface float, line or boat platform will greatly assist here
  • remove the unconscious divers mask to aid in air circulation and breathing.
  • Wait for the diver to regain consciousness (breathing, responsiveness to questions, etc)
  • Shallow Water Blackout response time is typically 3 – 10 seconds
  • Deep Water Blackout response time is between 10 – 30 seconds
  • Once the diver has recovered and breathing on their own, continued observation by the rescuer is important until out of the water. There is a possibility that the diver will surface and then blackout. Careful, detailed observation is required at all times by the rescuing entities involved.
  • All diving should be stopped for that day
  • If the diver does not respond and fails to start breathing on their own, begin the following:
  • Ditch all weights and masks from the unconscious diver and the rescuer.
  • Start basic first aid, arousal, open the airway and check for breathing
  • If the diver is not breathing, initiate the following procedures:
  • Signal for additional assistance
  • Begin performing artificial respiration (2 breaths initially, followed by 1 breath every 5 seconds)
  • Evacuate the diver from the water, either by towing to shore or to a boat
  • Once on shore or deck of the boat, continue maintaining airway control, artificial respiration, and check for a pulse. If no pulse is present, initiate CPR while continuing artifical respiration
  • Activate the planned EMS (Emergency Medical System)

It should be noted that training in First aid and CPR be a part of all those concerned in the dive activity. Your local dive shop can provide the training that not only covers basic first aid, but dive specific rescue techniques as well. In addition they can provide the training for administering O2 that can significantly increase the chances of recovery from submersed dive accidents.

Cliff Etzel
Cliff Etzel
Cliff is the former Freediving editor of He is now a freelance journalist and film-maker.


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