Association Internationale pour le Développement de l'Apnée – one of the main international freediving agencies


Cellular metabolism with oxygen, requiring oxygen for breathing

air embolism

Obstruction of the circulatory system caused by an air bubble as e.g.  as a complication from scuba diving [syn: aeroembolism] 2: pain resulting from rapid change in pressure [syn: decompression sickness, aeroembolism, caisson disease, bends]


Not aerobic    not needing or without oxygen –  an activity in which the body incurs an oxygen debt

anaerobic metabolism

Creation of energy through the combustion of carbohydrates in the absence of oxygen.

This occurs when the lungs cannot put enough oxygen into the bloodstream to keep up with the demands from the muscles energy. Generally  used for short busts of activity


From the Greek, it means "without, or not breathing".

ascent bo

Blacking out while ascending from a dive, if it happens, it's usually in the last 10 – 15 meters

ascent rates

Speed at which one ascends from a dive


An injury that results due to rapid or extreme changes in pressure.


Traditional swimming fins – one for each foot


Losing consciousness during breath-hold activities

blood PH

Level of acidity/alkalinity in the blood

blood shift

Related to the mammalian diving reflex - to prevent collapse under great pressure, the wall of the lungs fill with blood from other parts of the body.


See: Blackout

bottom time

Time spent underwater during a dive while freediving, or the time spent lingering at the bottomweight/plate


Part of the mammalian diving reflex: Slowing down of the heart rate and pulse

breathing oxygen

Breathing pure oxygen as a therapeutic measure or as a preparation for increasing one's time underwater.


Set of breathing procedures done before a long immersion – used to build up the capacity of the body in order to spend more time underwater on a single breath.

carp breathing

See: Packing

certifying agencies

Official freediving agencies that have the authority to certify the different local, national and world freediving records.

clogged ear

Having the ear canal of the outer ear obstructed, also called swimmers ear.


CMAS is an international organisation to promote SCUBA diving and other underwater sports. Founded by J.Y. Cousteau

CO2 narcosis

Toxicity resulting from too high levels of carbon dioxide in the blood

CO2 tolerance

Tolerance to carbon dioxide in the blood

collapsed lung

A collapsed lung, or pneumothorax, involves the collapse of the tissues of part or all of one lung so that oxygen cannot be absorbed into the blood stream in the normal way. Changes in pressure during diving may cause tissue damage. See also: pneumothorax

constant ballast

See: Constant weight

constant weight

One of the freediving disciplines: Diving down as deep as one can and ascending without the use of any mechanical device and rope. The weight of the freediver must remain the same during descent and ascent.


After a certain time without sufficient oxygen, the diaphragm starts to flutter and also experience contractions in order to "remind" the body that it needs to breath.

countdown time

The time just prior to a dive or static apnea. It is usually called out in a competition to help freedivers time their preparation and breath-up prior to the dive.


A sudden and involuntary tightening of a muscle – usually can be quite painful. Cramps usually happen in the legs for swimmers and freedivers.

Crazy Cuban

Diving as deep as possible with no aids whatsoever – no mask, fins, or weight belt. Also favoured by the freediver Sebastian Murat.


See: decompression sickness. Acronym for Decompression Illness


See: decompression sickness


Procedure used by scuba divers to reabsorb the nitrogen that has built up in the blood stream during long and deep dives

decompression chamber

A pressurized chamber used to reproduce the pressures found at great depths. Usually used to help divers recover from decompression sickness.

decompression sickness

Physiological disorder caused by a rapid decrease in atmospheric pressure, resulting in the release of nitrogen bubbles into the body tissues. It is also known as caisson disease, altitude sickness, and the bends

DEMA Dive Show

Diving Equipment & Marketing Association – Trade fair organization

depth adaptation

The capacity of the lungs to adapt to the pressure found at great depths.

fotos si


dive computers

Computer that can measure the depth and time spent at each depth. It also calculates the recommended decompression times needed by the diver.

diving response

Lowering of the heart rate and constriction of the blood vessels in the body causing blood to be redirected to the brain and heart to keep the important vital functions active.


Disorientation of the sense of balance – vertigo.

dry static

Static apnea on dry land.

dynamic apnea (with fins)

One of the disciplines of  freediving: swimming underwater as far as one can with fins.

dynamic apnea (without fins)

One of the disciplines of  freediving: swimming underwater as far as one can without any type of fins.

ear jamming

When the Eustachian Tubes close and no amount of pressure seems to open them during a dive


See: Air embolism

empty lung dives

Refers to "negative pressure dives" where freedivers prepare their lungs for very deep dives by emptying them of air and diving several meters. The lack of air pressure in the lungs simulates diving to a much greater depth and is useful as a warm up excercise


Balancing the air pressure in the middle and outer ear.


The act of equalizing the pressure difference between the middle and outer ear. There are several techniques. The two main ones are the Valsalva and the Frenzel techniques.

Eustachian tube

A tube that connects the middle ear with the nasopharynx and permits the equalization of pressure on both sides of the eardrum. It is bony and cartilaginous.


Freediving Regulations & Education Entity – Freediving teaching agency, less active

failure depth, breakpoint

The depth where lung pressure turns negative and below that it is difficult -or impossible- to bring air in the mouth for equalization

fire breathing

Slow shallow breathing, slowed by half closing epiglottis. The idea is to keep a nearly continuous 'greater-than-ambient' pressure in the lungs.

fluid goggles

Diving mask containing liquid instead if air to avoid using up valuable air equalizing the mask at depth. May have corrective lenses to adjust for the liquid the eyes have to see through.

free ascent dangers

The dangers of ascent, could be decompression sickness (rare in freedivers), shallow water blackout (most common danger), and overstretching of the lungs after having packed allot. (Also very rare)

free immersion

One of the disciplines of freediving: diving as deeply as one can without fins and pulling one's self down and up a guide rope.


The fine art of diving without using any breathing apparatus. Freediving can be competitive or recreational.

Frenzel Technique

Equalization technique involving using the tongue as a piston to force air through the Eustachian Tubes.


Protein in the red blood cells which combines with and carries oxygen around the body, and gives blood its red colour

heavy packing

Packing allot of air into the lungs – some freedivers can pack up to 4 liters of extra air into their lungs.

HMS Dolphin

A special 30 meter deep swimming pool in the UK designed for training submariners to escape from a submarine at 30 meters on a single breath. Freedivers can also use the HMS Dolphin paying a fee.

hook breathing

Taking a deep breath after a long breath–hold and bearing down on it for a couple of seconds to speed up the transfer of oxygen from the lungs to the rest of the body as well as to force blood up to the head and keep the O2 moving.

hyperbaric chamber

A pressurised chamber that allows for the delivery of oxygen in higher concentrations for therapeutic benefit – useful for decompression illness

hyperbaric oxygen therapy

The therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). It is considered effective treatment for air and gas embolisms as well as for decompression illness.


Too much carbon dioxide in the blood


Too much oxygen in the blood


Hyperventilation is the practice of excessive breathing with an increase in the rate of respiration or an increase in the depth of respiration, or both


Lower than normal carbon dioxide in the blood stream, can result from hyperventilation and bring on blackout sooner than normal.


When a person's body temperature falls below normal due to exposure to extreme cold. This is a dangerous condition that can result in death.

hypothermic diving system

System devised by Eric Fattah taking advantage of steep thermoclines to induce hypothermia therefore increasing the diving reflex to be able to dive deeper.


Lower than normal oxygen in arterial blood which gives rise to hypoxia.


Lower than normal oxygen supply to tissues even though there might be a proper amount of blood in the tissues.


International Association of Free Divers – Freediving teaching Agency, less active

lactic acid

Lactic acid is a by-product of anaerobic glycolysis and anaerobic metabolism. Although used as a fuel by the heart, excessive lactic acid slows down contractions of the skeletal muscles, preventing you from walking fast


Loss of Motor Control – also known as "samba". It occurs when the muscles have almost no oxygen and suffer seizures. It happens just before blackout.

lung fluid

Fluid i.e. plasma filling the walls (alveolis) of  your lungs is a response to the increased pressure at depth (usually at around 50m but it can vary quite a bit depending how much air you have in your lungs and your residual volume) to protect your lungs and other organs.

Lung packing

See: Packing

lung squeeze

See: pulmonary edema.

lung training

Training the lung to have more strength and capacity

lung volume

Amount of air in the lungs, also known as TLC

mammalian diving reflex

See: diving response

mask air

The amount of air in the mask. There are high–volume and low–volume masks. Freedivers prefer low–volume air as they are easier to equalize.

mask pumping

Technique for utilizing the air in one's mask during ascent. See: rebreathing

mask volume

See: Mask air

Middle-Ear Barotrauma

Middle–Ear problems due to quick changes in pressure. It can happen on ascent when the pressure in the outer ear diminishes faster than in the inner ear. Also known as "reverse squeeze".


Fins based on the design of a dolphin's tail. Both feet fit into a single monofin. Even though hard to use at first, they provide greater power and speed than bi–fins.

N2 narcosis

See: nitrogen narcosis


See: nitrogen narcosis

negative pressure dives

See: Empty lung dives


Someone new to a particular activity, a beginner

nitrogen narcosis

Mental state similar to euphoria, drunkenness and disorientation caused by the narcotic effects of the air's nitrogen at high pressure. Divers often exhibit dangerous behaviour such as ditching equipment underwater. Also known as rapture of the deep.

no limits

One of the disciplines of freediving: Descending as far as possible with ballast equipment (usually a sled) and ascending with an air balloon or similar.

nose clip

Device that closes the nostrils to prevent water getting in or air getting out.

O2 levels

Levels of oxygen in the blood

oxygen narcosis

See: oxygen toxicity

oxygen toxicity

Occurs when one breathes high partial levels of oxygen in the blood stream. Symptoms can be deep fatigue while breathing, muscular twitching, anxiety, confusion, incoordination, and convulsions including visual and auditive abnormalities

pack stretching

Stretching of the lungs due to packing


Special techniques for filling the lungs with more air than normally possible.


Partial pressure of arterial carbon dioxide in the blood


Acronym for "Personal Best"

peripheral vasoconstriction

It has been shown that at depth, blood flow is shunted from the limbs to those organs whose oxygen consumption is critical, the heart and brain

personal bests

One's best record in any of the disciplines of freediving

pipe mask

Diving mask with a small tube extending from the mask to mouth for equalizing.


A condition in which air or other gas is present in the pleural cavity and which occurs spontaneously as a result of disease or injury of lung tissue or puncture of the chest wall or is induced as a therapeutic measure to collapse the lung. See also: Collapsed lung


Training instrument used for enhancing lung capacity.


Yogic breathing techniques for balancing and enhancing the body's vital energies.

pulmonary edema

Dangerous medical condition where the lung fills with increased interstitial fluid causing the alveoli to flood with the fluid and be coated in blood, thus reducing the alveoli's capacity to transfer oxygen.


In relation to freediving: Sniffing or rebreathing the expanding air in one's mask while ascending. Also known as "mask pumping"

recreational freediving

Freediving for pure and simple fun!

residual lung volume (RV)

The volume of air that remains in the lungs after exhaling completely

Reverse Squeeze

See: Middle–Ear Barotrama


See: Residual lung volume


"Specialized Advanced Freediving Enhancement & Reliability " –  Freediving teaching agency, less active


Loss of muscle control commonly known as “samba”,  preceding blackout in many cases.


Saturation of Oxygen (arterial blood)

security rope

Guide rope or line used to orient the freediver while descending, also known as the rope or the diverope.

shallow water blackout

Sudden loss of consciousness caused by pressure drop in oxygen.


Swimming underwater or on the surface usually with the help of a face mask, fins, and a snorkel

solo freediving

Freediving alone without a buddy


Medical instrument used to measure vital lung capacity


Having a buddy watch you for safety reasons while engaging in freediving activities either in the swimming pool or the sea.

static apnea

One of the disciplines of freediving: Seeing how long one can hold one's breath while floating on the surface with the face submerged.

suit squeeze

"Suit squeeze", where the hood of a stretchy wetsuit 'seals' around the outer ear, trapping air in the outer ear. This can cause problems due to incorrect equalizing on descent or ascent.

surface intervals

Time spent at the surface between dives


See: Shallow water blackout

tear duct equalization

Equalization (of the mask?) through the tear ducts

tidal volume

The volume of air normally inhaled or exhaled when one is making no extra effort.


See:Total Lung Capacity

total lung capacity (TLC)

Total Lung Volume: The sum of RV and VC

variable ballast

One of the freediving disciplines: Going down with a weighted device and coming up pulling on a rope or swimming


See: peripheral vasoconstriction


See: Vital Capacity


More than normal breathing, less than hyperventilation.

vital capacity (VC)

The amount of air of a complete and full exhalation including the expiratory reserve volume

warm ups

Preparative exercises previous to an activity requiring great physical effort. Usually different kind of dives.

weight belt ditching

Releasing the weight belt


Applying the correct amount of weight for one's freediving or scuba needs


Usually lead weights used for counteracting the body's (and wetsuit's) natural buoyancy.

wet lung

Also known as Pulmonary Edema: The abnormal accumulation of liquids in the lungs due to rapid changes in pressure. Different from lung fluid, this is harmful and can lead to secondary drowning.

wet statics

Static apnea in the pool or sea


Adrian Valls (edited by Sebastian Näslund)