Freediving has its own terminology that can be confusing for beginners at first. What does the Frenzel maneuver mean? How does CWT differ from CNF? And what exactly is samba?
In this glossary, you will find explanations of all the basic terms used in freediving – from techniques and disciplines through equipment to physiological processes. Each term is explained clearly and concisely so you can quickly grasp the essence.
Use the navigation above for quick access to the letter you’re looking for.
🤿 Quick alphabetical navigation
A
Acidosis (Respiratory acidosis)
A shift in acid-base balance toward lower pH, mainly caused by CO₂ accumulation during breath-holding. Contributes to the “urge to breathe” sensation.
Adaptation to CO₂ (CO₂ tolerance)
The ability to tolerate higher levels of CO₂ without panic and unnecessary stress. Improves through training (CO₂ tables, relaxation techniques, working with contractions).
Alkalosis (Respiratory alkalosis)
A shift in pH upward due to decreased CO₂, typically after hyperventilation. Delays the urge to breathe but increases the risk of hypoxic blackout.
Apnea
Voluntary breath-holding. The fundamental principle of freediving – allows staying underwater without breathing apparatus.
Ascent
The phase of the dive moving toward the surface. Critical phase from a safety perspective (common time for hypoxia/blackout).
B
Barotrauma
Umbrella term for pressure injuries (ear, sinuses, mask, lungs). In practice, it’s useful to distinguish: ear/sinus/mask/lung barotrauma.
Bi-fins
Long freediving fins used in pairs. Efficient, universal choice for pool and depth.
Blackout (BO)
Loss of consciousness due to lack of oxygen (hypoxia). In practice, often occurs on ascent or shortly after surfacing.
Blood shift
Transfer of blood to the chest and lungs at depth as part of the dive response, helps compensate pressure and protect the lungs.
Bradycardia
Slowing of heart rate as part of the dive response. Reduces oxygen consumption.
Breath-hold
Voluntary cessation of breathing (apnea) – the foundation of freediving.
Buddy
Safety partner monitoring the diver. Basic rule: never dive alone.
Buoy (Surface buoy)
Float with flag and attachment for line. Increases safety, visibility, and provides surface support.
Buoyancy
Upward force acting on a submerged body. Freedivers adjust it with weights, wetsuit, and lung air volume.
C
CNF (Constant No Fins)
Depth discipline without fins – movement using body strength only.
CO₂ tolerance
The ability to tolerate higher levels of CO₂ without panic and unnecessary stress. Improves through training (CO₂ tables, relaxation techniques, working with contractions).
Comfort zone
Subjective range where the diver feels calm and in control. Safe progression is gradually expanding the comfort zone without pushing too hard.
Compression
Decrease in air volume with depth (Boyle’s law) – affects lungs, mask, ears, and buoyancy.
Contraindications
Conditions where freediving is risky (e.g., certain cardiac arrhythmias, epilepsy, untreated lung problems, acute infections, pregnancy, etc.). Individual assessment by a physician with diving knowledge is always advisable.
Contractions
Involuntary contractions of the diaphragm and respiratory muscles with rising CO₂. They are a normal body signal, not a reason to panic.
Counterweight system
Safety system on the line that allows quick retrieval of the diver in emergency.
CWT (Constant Weight)
Depth discipline: descent and ascent with the same weight, using monofin or bi-fins.
CWTB (Constant Weight Bi-Fins)
CWT variant with bi-fins.
D
DCS / DCI (Decompression Sickness / Decompression Illness)
Decompression illness from inert gases. Rare in freediving, but risk increases with repeated deeper dives, short surface intervals, and high cumulative load.
DNF (Dynamic No Fins)
Pool discipline: distance underwater without fins.
Duck dive
Technique for diving from surface: forward bend, head down, legs above surface, kick and transition to descent.
DYN (Dynamic Apnea)
Pool discipline: distance underwater with fins (monofin or bi-fins).
DYNB (Dynamic Bi-Fins)
Dynamic variant with bi-fins.
E
Ear barotrauma
Ear injury from pressure (middle or inner ear). Can occur with improper/late equalization.
Equalization
Equalizing pressure in ears, sinuses, and mask during descent (and sometimes ascent). Essential for safety.
Eustachian tube
Connection between middle ear and nasopharynx. Opens during pressure equalization.
Exhale dive
Dive with less air in lungs (e.g., FRC dives). Used for training, has specific risks and benefits.
F
FIM (Free Immersion)
Depth discipline: diver moves along the line using hands without fins.
Fluid goggles
Goggles filled with liquid (instead of air), minimize the need to equalize mask volume.
FRC (Functional Residual Capacity)
Volume of air in lungs after normal exhalation. In practice, “FRC dive” is used as a specific training type of dive.
Freediving computer
Measures depth, time, surface intervals, alarms (depth/time/speed), dive log.
Freediving fins
Long fins optimized for efficient movement (bi-fins or monofin).
Freediving line
Line with meter markings and weight (bottom weight). Serves for orientation and safety.
Freediving training
Systematic preparation: apnea, technique, relaxation, swimming, equalization, safety procedures, and load planning.
Freediving wetsuit
Wetsuit often without zipper, often with open-cell interior for better seal and insulation.
Freefall
Phase of depth dive when freediver descends without kicking due to negative buoyancy – energy-efficient phase.
Frenzel (Frenzel maneuver)
Pressure equalization technique using tongue and pharyngeal muscles. Standard for freediving.
H
Harpoon (Speargun)
Tool for underwater hunting. In freediving context, includes safety rules (buddy, buoy, lines).
Hood (Neoprene hood)
Neoprene hood/cap to reduce heat loss.
Hook breathing
Recovery breathing after surfacing with a short “hold”/”hook” after inhalation for pressure stabilization and oxygenation (mainly used in competition).
Hypercapnia
Elevated CO₂ level in blood. Is the main trigger of “urge to breathe”.
Hyperventilation
Excessive breathing reducing CO₂ (hypocapnia). Dangerous – delays warning signals and increases blackout risk.
Hypocapnia
Decreased CO₂ level typically after hyperventilation. Reduces warning signals, increases risk of hypoxia without warning.
Hypoxia
Low O₂ level in tissues. In freediving can lead to LMC or blackout.
I
Immersion
The act of submersion itself triggers part of the dive response (especially with cold and face in water).
IRV (Inspiratory Reserve Volume)
Additional volume that can be inhaled after normal inhalation.
K
Knife / Line cutter
Safety tool against entanglement (nets, fishing lines, rope).
L
Lanyard (Safety lanyard)
Connection of freediver to line – prevents loss in current, aids in rescue.
Laryngospasm
Reflex contraction of vocal cords that may briefly limit water entry into airways – cannot be relied upon as protection.
LMC (Loss of Motor Control)
Loss of motor control (uncontrolled twitches, “samba”). Warning state just before blackout.
Lung squeeze (Pulmonary barotrauma)
Lung barotrauma at depth (with high compression and inappropriate dive). May manifest as coughing, pain, coughing up blood.
M
Mammalian Dive Response (MDR)
Set of reflexes (e.g., bradycardia, peripheral vasoconstriction, blood shift) activated by apnea and immersion, supports oxygen conservation.
Mask (Low-volume mask)
Mask with small internal volume – less air to equalize (mask equalization), often preferred.
Mask squeeze
Barotrauma from not equalizing pressure in mask during descent (negative pressure in mask).
Monofin
One fin for both feet. Efficient dolphin kick (CWT/DYN).
Mouthfill (Mouthfill equalization)
Advanced equalization technique: creating an air “reserve” in the mouth and dosing it for equalization in deeper phases of dive (often when diving “beyond RV”).
N
Narcosis (Nitrogen narcosis)
Altered state of consciousness at high partial pressure of nitrogen (in very deep dives) – may impair judgment and coordination.
Negative buoyancy
State when diver sinks without kicking. Used in freefall.
Neoprene
Material and generally “suit” for insulation and protection.
NLT (No Limits)
Discipline: descent with weight, ascent with buoyancy device/balloon assistance.
Noseclip
Device closing the nose (pool and depth). Often in combination with goggles.
O
O₂ tolerance
Ability to work at low O₂ levels without panic (simplified). In reality, it’s a combination of physiology, technique, psychology, and safe training.
Overtraining (OT)
Training overload (physical and nervous). In freediving often leads to worse relaxation, higher O₂ consumption, performance stagnation.
P
Packing (Lung packing)
“Packing” air into lungs using mouth/pharynx above normal TLC. Advanced and potentially risky (pressures, barotrauma), requires guidance and caution.
PB (Personal Best)
Personal record (time, distance, depth).
Peripheral vasoconstriction
Narrowing of vessels in extremities – redirects blood to vital organs (part of MDR).
Pulmonary edema (White lungs)
A condition with fluid in the lungs (e.g., after intense performance/deep dives). May manifest as coughing, shortness of breath, sometimes pink foamy sputum.
Purge breathing
Slightly deepened, controlled breathing before apnea without hyperventilation. Goal: calm down, not “blow out CO₂”.
R
Recovery breathing
Short series of controlled breaths after surfacing for O₂ stabilization and reducing risk of post-hypoxic issues.
Relaxation
Key skill: reducing tension, stress, and oxygen consumption (mental and physical).
Reverse block
Blockage on ascent (air from ear cannot escape due to Eustachian tube). Painful, risky – resolved by stopping, gentle techniques, possibly ending dive.
RV (Residual Volume)
Residual volume – air remaining in lungs even after maximum exhalation (individual, often stated as approximately ~20–25% of TLC).
S
Samba
Colloquial term for LMC (typical “dance-like” twitches).
Shallow Water Blackout (SWB)
Blackout in shallow depth or on surface, typically on ascent/after surfacing (often after hyperventilation or pushing performance).
Sinus squeeze
Sinus barotrauma from pressure non-equalization.
Sled
Device used in NLT/VWT for descent.
Snorkel (Freediving snorkel)
Simple, soft snorkel without valves. Often removed/not worn in mouth during dive.
Soft palate
Important in advanced equalization (separation of nasal/oral cavity, control of “closures”).
Splenic contraction
Part of dive response: spleen can release some red blood cells and temporarily increase O₂ transport capacity.
STA (Static Apnea)
Pool discipline: maximum breath-hold time while stationary on surface.
Surface interval
Rest on surface between dives – for O₂ recovery, CO₂ removal, and reducing cumulative load.
Surface protocol (SP)
Competition procedures after surfacing: remove all “facial equipment” (mask/goggles/noseclip), show OK, and say “I’m OK” within time limit (often 15 seconds per rules).
Surface support
Safety organization on surface (buddy, safety, buoy, communication, dive plan).
T
Tag
Tag at end of line; in some competition formats, proof of depth achieved.
Taravana
Syndrome of neurological symptoms with repeated breath-hold deep dives, often described as a specific form of decompression illness (DCS/DCI) with cumulative load.
TLC (Total Lung Capacity)
Total lung capacity after maximum inhalation (VC + RV).
TV (Tidal Volume)
Breath volume during quiet breathing.
U
Urge to breathe
Feeling of need to breathe mainly caused by CO₂ rise (not directly O₂ drop). Important for mental control and safe training.
V
Valsalva
Pressure equalization by exhaling against closed nose. For freediving often less suitable than Frenzel (more demanding at depth, less relaxed).
Vasoconstriction
Vessel narrowing – general term; in freediving mainly peripheral vasoconstriction as part of MDR.
VC (Vital Capacity)
Vital lung capacity – volume that can be exhaled after maximum inhalation.
VWT (Variable Weight)
Discipline: descent with weight, ascent under own power (fins/line) without weight.
W
Warm-up
Preparatory apneas/dives before performance. Not a “necessity” but a tool; excessive warm-ups can worsen performance.
Weight belt (Freediving belt)
Rubber/rubberized belt for lead weights – holds stably even with changes in wetsuit volume.
Weights
Lead weights on belt or neck weight for pool.
Wetsuit (Freediving wetsuit)
Wetsuit for thermal insulation and protection, often without zipper for freediving.