Emergency Ascent

Emergency Ascent

Controlled Emergency Swimming Ascent (CESA) (aka "blow and go") is a technique used by scuba divers as a safety measure when a diver has run out of breathing gas in shallow water and must return to the surface. One of the scariest things that can happen to a Scuba diver is an uncontrolled ascent either intentionally initiated in an emergency or by unintentionally often caused by faulty Scuba equipment.

An uncontrolled ascent is also known as an Emergency Swimming and Emergency Buoyant Ascents which is always an unplanned ascent, where a diver aborts a dive due to equipment problems, out-of-air situation, or injury to self, or another diver which are intentionally initiated emergency ascents or unintentionally initiated ascents (also known as a buoyant ascent) when a diver can loses buoyancy and quickly get into an uncontrolled ascent by loss of weights or by a malfunctioning BCD often a sticky inflator causing the diver to ascend. The technique involves simply ascending at a controlled pace, while exhaling slowly or vocalizing a continuous sound.

As the diver ascends, the pressure in the lungs increases relative to surrounding water pressure. Exhaling serves to equalize this difference. Hence, the diver can continue exhaling throughout the ascent, and still have air in their lungs at the surface. For the same reason, if the diver fails to exhale during the ascent, lung over expansion injury is likely to occur. As the diver swims to the surface (making the ahhhhh sound) they will feel as if they are not running out of breath; this is because the compressed air they inhaled at depth is expanding as they ascend.

Avoiding an Emergency Ascent


  1. The most common cause of an emergency while diving is panic due to an unfamiliar environment and the complexities of unfamiliar equipment. Novice divers should dive repeatedly to shallow depths (30ft) under all sorts of conditions. Dive instruction is available from licensed dive professionals worldwide. You should never dive without an experienced dive buddy, with unfamiliar equipment, or at a site you have not evaluated and researched carefully.
  2. Emergency ascents are most often the result of running out of air in your tank. Modern tank and regulator systems usually have a reserve, but the urge to push the limits, or stay just a little bit longer has tricked even experienced divers into running out of air. Play it safe, watch your pressure gauge, and adhere to the planned dive schedule.
  3. The second most common cause of an emergency ascent is a real or perceived equipment failure. Always be thoroughly familiar with all your dive equipment prior to entering the water. Always stay with your buddy during a dive, and if an equipment failure does occur, switch to buddy breathing (or use an octopus rig if available). Take a few moments to confirm that you really do have an equipment failure. If the failure is real, make a normal ascent while buddy breathing.

Always dive with an octopus rig if available. Buddy breathing can be difficult in an emergency situation.

It can't be said too many times: NEVER dive alone.

Emergency Swimming Ascent


  1. An emergency swimming ascent can be very safe. It is essentially a normal ascent, except presumably you are not getting any air from your tank. You can change your rate of ascent and your buoyancy as you swim to the surface.
  2. Start moving towards the surface by pushing off the bottom or kicking strongly a few times with your fins.
  3. Continue towards the surface while swimming as calmly as possible and maintaining a normal rate.
  4. Look up at all times while ascending. This not only allows you to look for obstructions or boats on the surface, it also extends your neck and helps you keep your airway open.
  5. Try to breath from your regulator normally as you move towards the surface. The pressure drop as you rise towards the surface can give you a feel more breaths from an empty tank.
  6. Be ready to release your weight belt if you are not ascending at a normal rate.
  7. Once on the surface, inflate your buoyancy compensator completely. Remove your regulator, and signal for assistance if needed.


  • You can remove your weight belt and hold it in your hand so that you can drop it more quickly if needed.
  • You can also use the emergency inflation system on your buoyancy compensator, but it is better if you can swim normally to the surface. See the Emergency Buoyant Ascent section below.


  • Never hold your breath (or exhale completely) while doing any kind of ascent. As you rise to the surface, the volume of air remaining in you lungs will increase as the pressure drops. You should be able to exhale slowly all the way to the surface.
  • Sixty feet per minute is the recommended safe rate of ascent.

Emergency Buoyant Ascent


  1. An emergency buoyant ascent is typically very rapid. You will have farmless control over your rate of ascent then with the swimming ascent described above. This rapid ascent can expose you to the dangers of decompression sickness and air embolism. The emergency buoyant ascent should be your last ditch option, but it will get you to the surface and keep you there.
  2. To start a buoyant ascent, inflate your buoyancy compensator and drop your weight belt. Use your emergency inflation system if needed.
  3. Look towards the surface to open your airway and breath out constantly. The more rapidly you are ascending, the more rapidly the air in your lungs will expand.
  4. As you rise towards the surface, release air from your buoyancy compensator to provide some control of your ascent. With your weight belt gone you will rise rapidly regardless.
  5. About 20 feet from the surface, spread your arms and arch your back until your body is almost parallel to the surface. This will create more drag and slow you down before you reach the surface.
  6. Once on the surface, inflate your buoyancy compensator completely. Remove your regulator, and signal for assistance immediately. You may feel fine initially, but decompression sickness symptoms may begin to affect you without warning.

Never, never, never hold your breath while ascending, especially during a rapid buoyant ascent.

Last Updated on Friday 17th December 2010