Index of underwater diving: L–N

Last updated February 18, 2025

The following index is provided as an overview of and topical guide to underwater diving: Links to articles and redirects to sections of articles which provide information on each topic are listed with a short description of the topic. When there is more than one article with information on a topic, the most relevant is usually listed, and it may be cross-linked to further information from the linked page or section.

A human activity – intentional, purposive, conscious and subjectively meaningful sequence of actions. Underwater diving is practiced as part of an occupation, or for recreation, where the practitioner submerges below the surface of the water or other liquid for a period which may range between seconds to order of a day at a time, either exposed to the ambient pressure or isolated by a pressure resistant suit, to interact with the underwater environment for pleasure, competitive sport, or as a means to reach a work site for profit or in the pursuit of knowledge, and may use no equipment at all, or a wide range of equipment which may include breathing apparatus, environmental protective clothing, aids to vision, communication, propulsion, maneuverability, buoyancy control and safety equipment, and tools for the task at hand.

There are seven sub-indexes, listed here. The tables of content should link between them automatically:

L

Contents: Top	0–9	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z

Section contents: Top of section, La, Le, Li, Lo, Lr, Lu–Ly

La

Ladder pattern search – Search pattern with evenly spaced parallel legs
Lambertsen Amphibious Respiratory Unit (LARU) – Early closed circuit oxygen diving rebreather
Lambertsen, Christian J. – American medical researcher (1917–2011)
LAR-5 – Military oxygen tebreather by Drägerwerk
LAR-6 – Military oxygen rebreather by Drägerwerk
LAR-V – Military oxygen rebreather by Drägerwerk
Laryngospasm – Involuntary contraction of the vocal folds restricting inhalation
The Last Dive – Non-fiction book by Bernie Chowdhury about a double wreck diving fatality
Latent hypoxia – Lung gas and blood oxygen concentration sufficient to support consciousness only at depth
Launch and recovery system (diving) – Equipment used to deploy and recover a diving bell, stage, or ROV
Lazy shot – A diving shotline which does not reach the bottom

Le

Section contents: Top of section, La, Le, Li, Lo, Lr, Lu–Ly

Legal aspects of underwater diving , also known as legal aspects of diving – How diving activities are affected by law
Le Prieur, Yves – French naval officer and inventor of a free-flow scuba system

Li

Section contents: Top of section, La, Le, Li, Lo, Lr, Lu–Ly

Life-support equipment – Equipment which is necessary to support life in a hostile environment
Life support supervisor – Senior life support technician
Life support technician – A member of a saturation diving team who operates the surface habitat
Life-support system – Technology that allows survival in hostile environments
Life support system operation – Operation of the systems which are necessary for the survival of the occupants
Lifeline (diving) – A rope connecting the diver to an attendant, usually at the surface
Lifting bag – Airtight bag used for underwater buoyant lifting when filled with air
Light head – Dive light with cable power supply from a battery canister
Lightweight demand diving helmet , also known as lightweight demand helmet – Diving helmet supported by the head and neck
Lightweight diving helmet – Diving helmet supported by the head and neck
Limpet mine – A type of naval mine which is attached to a target by magnets
Line arrow – Marker used on cave guide lines to provide safety information to divers
Line holder – Simple device for storing and deploying line underwater
Line marker – Marker used on cave guide lines to provide safety information to divers
Lipid – Substance of biological origin that is soluble in nonpolar solvents
Liquid breathing – Respiration of oxygen-rich liquid by a normally air-breathing organism
List of British records in finswimming
List of Commonwealth records in finswimming
List of DAN publications – List of Divers Alert Network publications
List of designations under the Protection of Wrecks Act – All sites designated under the UK Protection of Wrecks Act
List of diver certification organisations – Agencies which issue certification for competence in diving skills
List of diver certification organizations – Agencies which issue certification for competence in diving skills
List of Divers Alert Network publications
List of diving environments by hazard – Example types of a class of diving hazard
List of diving environments by type – Variety of environments that people may dive in
List of diving hazards and precautions – Hazards associated with underwater diving
List of European records in finswimming
List of freediver training agencies – Organisation setting standards and providing certification for freedivers
List of legislation regulating underwater diving – List of national and state legislation regulating underwater diving
List of military diving units
List of notable scuba divers – List of biographical articles about scuba divers
List of recreational scuba diving certification agencies – Organisations providing training standards and certification for recreational scuba diving
List of researchers in diving physiology and medicine
List of researchers in underwater diving – People who made discoveries or inventions in the science or technology of underwater diving
List of scuba divers – Hierarchical outline list of biographical articles about underwater divers
List of shipwrecks in international waters
List of shipwrecks of Africa
List of shipwrecks of Asia
List of shipwrecks of Europe
List of shipwrecks of Hong Kong
List of shipwrecks of North America
List of shipwrecks of Oceania
List of shipwrecks of South America
List of shipwrecks of the Isles of Scilly
List of shipwrecks of the Isles of Scilly (19th century)
List of signs and symptoms of diving disorders – Evidence of physiological disorders resulting from underwater diving
List of types of diving environments – Variety of environments that people may dive in
List of undersea explorers
List of underwater divers – List of underwater divers whose exploits have made them notable.
List of underwater diving environments – Variety of environments that people may dive in
List of underwater diving equipment manufacturers – Current and historic manufacturers of equipment specifically intended for use for underwater diving
List of underwater diving hazards and precautions – Hazards associated with underwater diving
List of underwater explorers
List of United States Navy SEALs – Notable members of the US Navy SEALs and UDTs
List of United States records in finswimming
List of world records in finswimming
List of wreck diving sites – List of shipwreck sites which are popular amongst scuba divers for wreck diving.
Lists of shipwrecks – Index to Wikipedia's lists of shipwrecks
Little Blue Lake – Flooded sinkhole dive site in South Australia
Live-boat diving – Diving from a boat which is under way (not moored)
Live-boating – Diving from a vessel under way
Liveaboard dive boat , also known as liveaboard – Vessel providing support for diving tourists

Lo

Section contents: Top of section, La, Le, Li, Lo, Lr, Lu–Ly

Lobster hook – Implement for extracting lobsters from holes
Localised pressure differential – Area with strong flow caused by a local pressure differential
Lock-in (diving) – Enter an enclosed environment at a different pressure to ambient through an air-lock
Locking collar (diving helmet) – Component to prevent accidental removal of a diving helmet
Lock-off – Split a secure airtight connection between two pressurised chambers via an airlock
Lock-on (diving) – Make a secure airtight connection between two pressurised chambers via an airlock
Lock-out (diving) – Exit an enclosed environment at a different pressure to ambient through an air-lock
Lockout–tagout (LOTO) – Safe isolation of dangerous equipment during maintenance or testing
London Diving Chamber Dive Lectures – Series of public lectures that have been hosted at the Royal Geographical Society in London
Long distance part of the 2011 Finswimming World Championships – International competition in Hódmezővásárhely, Hungary
Long hose regulator – Hose which allows two divers sharing gas to swim though a restriction
Long term effects of underwater diving – Effects of long term exposure without clinical symptoms
Long term health effects of diving – Effects of frequent underwater diving on health
Long-Term Mine Reconnaissance System – American torpedo tube-launched underwater search and survey unmanned undersea vehicle
Longshore current – Inshore current running parallel to the shoreline
Longshore drift – Sediment moved by the longshore current
Loop flush – Rebreather diving safety procedure
Loop rebreather – Rebreather architecture with one-way flow
Loss of the continuous guideline – Separation from the line marking the way out of a diving penetration
Lost buddy procedure – Standard procedure for dive buddy separation
Lost guide line – Scuba penetration diving emergency
Low energy coast – Shoreline protected from high energy waves
Low Impact Diver – PADI specialty to improve poor buoyancy, trim and finning skills in recreational divers
Low impact diving – Scuba diving that has minimal environmental effect
Low pressure breathing air compressor – Machine to provide atmospheric air at low pressure for breathing
Low visibility (diving) – Water conditions in which objects cannot be seen for a long distance
Low visibility diving – Diving in a turbud diving medium

Lr

Section contents: Top of section, La, Le, Li, Lo, Lr, Lu–Ly

LR5 – Crewed submersible for submarine rescue
LR7 – Crewed submersible undersea rescue vehicle

Lu–Ly

Section contents: Top of section, La, Le, Li, Lo, Lr, Lu–Ly

Lung over-pressure injury – Damage to lungs caused by internal overpressure
Lung overexpansion injury – Injury to the lungs caused by excessive internal pressure
Lung overpressure injury – Injury to the lungs caused by excessive internal pressure
Lunocet – Biomimetic monofin
Luxfer – Multinational manufacturer of seamless aluminium pressure vessels
Lyons Maritime Museum – Diving history museum in St. Augustine, Florida

M

Contents: Top	0–9	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z

Section contents: Top of section, Ma, Mc–Me, Mi–Mk, Mn–Mo, Ms–Mv

Ma

Macro life – Organisms suitable for macro photography
Macro photography – Photography genre and techniques of extreme close-up pictures
Magnesium torch – Bright light source made from magnesium, which burns underwater
Man in the Sea Museum – Diving history museum in Panama City Beach, Florida
Management of multiple cylinders – Techniques for carrying and using multiple scuba sets
Manifold (scuba) – Component to functionally connect scuba cylinders
Manifolded twin scuba set , also known as manifolded twin set or manifolded twins – Two scuba cylinders functionally connected by a manifold
Manta ray night dive – Ecotourism diving experience
Manually controlled closed circuit rebreather – Rebreather in which the oxygen content of the loop gas is controlled by the diver
MARCOS – Indian Navy special operations force
Mares (scuba equipment) – Italian manufacturer of underwater diving equipment.
Marine Commandos – Marine special operations group of the Lebanese Army
Marinejegerkommandoen – Norwegian naval special operations unit
Maritime archaeology – Archaeological study of human interaction with the sea
Maritime archaeology in Australia – Study of Australia's underwater heritage
Maritime Archaeology Sea Trust – Charitable trust in the UK
Maritime Archaeology Trust – Charitable organization in Great Britain
Mark IV Amphibian – British military oxygen rebreather
Mary Rose – English Tudor warship (1511–1545)
Mass fraction blending – Mixing gas by measuring added mass of each component
Master diver (United States Navy) – Senior diver rating in US Navy
Master Instructor – Grade of recreational dive instructor with some experience
Master Scuba Diver – The highest non-leadership recreational scuba diver certification issued by some agencies
Maximum operating depth – Depth below which the partial pressure of oxygen (pO2) of the gas mix exceeds an acceptable limit
Maximum voluntary ventilation – Limit of amount than can be breathed in a minute
Maya AUV India – Autonomous underwater vehicle from National Institute of Oceanography, India

Mc–Me

Section contents: Top of section, Ma, Mc–Me, Mi–Mk, Mn–Mo, Ms–Mv

McCann Rescue Chamber – Diving bell for rescuing submariners
Mechanical dead space – Space in breathing apparatus in which the breathing gas must flow in both directions
Mechanism of diving regulators , also known as mechanism of the diving regulator – Arrangement and function of the components of regulators for underwater diving
Media diver – Professional diver working in the media sector
Media diving – Underwater diving in support of the media industries
Medical Examiner of Divers – Doctor registered as competent to assess medical fitness to dive
Medical fitness to dive – The medical fitness of a person to function safely underwater under pressure
Medical oxygen – Oxygen used for therapeutic purposes
Medical plastic oxygen mask – Disposable mask for providing oxygen therapy
Medically fit to dive – State of a person who has no medical constraints preventing them from underwater diving
Membrane gas separation – Technology for splitting specific gases out of mixtures
Messenger line – Light line used to pull heavier cable or lower a package along a downline
Metabolism – Set of chemical reactions in organisms
Metre sea water , also known as metre seawater – Unit of pressure equal to one tenth of a bar

Mi–Mk

Section contents: Top of section, Ma, Mc–Me, Mi–Mk, Mn–Mo, Ms–Mv

Micropore scrubber cartridge – Carbon dioxide absorptive cartridge
Middle ear barotrauma – Pressure injury to the middle ear
Midwater , also known as mid-water – In the water column between surface and bottom
Midwater downline – A weighted line suspended from a floating support in deep water
Military diver – Underwater diver of a military unit
Military diver training – Training of underwater divers for service in the armed forces
Military diving – Underwater diving in a military context by members of an armed force
Mills, Linnea – Diver who drowned during a PADI training dive
Mine escape set – Portable breathing apparatus intended for escape from compromised mines
Minedykkerkommandoen – Norwegian Navy clearance diver unit
Minentaucher – Mine clearance divers of the German Navy
Minimum gas principle – Minimum breathing gas for safe ascent for given depth and time to surface
Minimum operating depth – Depth above which the oxygen concentration is too low to breathe safely
Mini Rover ROV – Small, low cost observation class remotely operated underwater vehicle
Mir (submersible) – Self-propelled deep submergence vehicle
Missed decompression – Unsafe adcent from dive
Mission 31 – An undersea expedition organized by Fabien Cousteau
Mitchell, Simon – New Zealand physician and author on diving medicine
Mitigation – Reduction of something harmful or the reduction of its harmful effects
Mixed gas (diving) – Breathing gases mixtures blended for use in underwater diving
Mixed gas rebreather – Rebreather using gas other than only oxygen
Mk 1 Underwater Defense Gun – Underwater firearm developed by the United States during the Cold War
MK V Deep Sea Diving Dress – Standard diving dress of the US Navy
Mk V Mod 1 Heliox helmet – US Navy standard diving helmet modified for heliox

Mn–Mo

Section contents: Top of section, Ma, Mc–Me, Mi–Mk, Mn–Mo, Ms–Mv

MN90 decompression tables , also known as Table Marine National MN90 – French navy decompression tables
Mode of diving – The conceptual methods of underwater diving
Modulated ultrasound – Technology for transmitting signals through water
Moir, Ernest William – British civil engineer credited with inventing the first medical airlock
Molecular diffusion – Thermal motion of liquid or gas particles at temperatures above absolute zero
Momsen, Charles – US Navy admiral, submarine rescue (1896–1967)
Monkey diving – Sidemount diving with a single cylinder
Monofin – Single blade swimfin attached to both feet
Moon pool – Opening in the base of a hull, platform, or chamber giving access to the water below
Morse Diving – American manufacturer of diving equipment
Morse Engineering Mk 12 helmet – US Navy deep water free-flow helmet
Motion sickness – Nausea caused by motion or perceived motion
Motorised Submersible Canoe – WWII British frogman delivery vehicle
Mouth-to-mouth resuscitation – Artificial ventilation using exhaled air from the rescuer
Mouthpiece (breathing apparatus) – Respiratory user interface
Mouthpiece retaining strap – Safety item for scuba diving, particularly with a rebreather

Ms–Mv

Section contents: Top of section, Ma, Mc–Me, Mi–Mk, Mn–Mo, Ms–Mv

MSDS Marine – British marine and coastal archaeological contractor
MSM-1 – Italian deep-submergence rescue vehicle
Msw – Metre of sea water, a unit of pressure
Muck diving – Recreational diving on a loose sedimentary bottom
Multi-level dive – Scuba diving in consecutively shallower depth ranges on one dive
Muscle memory , also known as muscle-memory – Consolidating a motor task into memory through repetition
Mushroom valve (diving) – Rubber non-return valve
M-value (decompression) – Maximum inert gas supersaturation allowed for a tissue in decompression theory}

N

Contents: Top	0–9	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z

Section: Top of section, Na, Ne, Ni, No, Nu

Na

Namibian Marine Corps – Combat body created in 2016
National Academy of Scuba Educators (NASE) – Recreational scuba training and certification agency
National Association for Cave Diving (NACD) – American non-profit organization for improving cave diving safety
National Association of Underwater Instructors (NAUI) – Non-profit training and certification agency association of scuba instructors
National Board of Diving and Hyperbaric Medical Technology – Non-profit organization for education and certification in diving and hyperbaric medicine
National Diving and Activity Centre – Flooded quarry in Gloucestershire used as a recreational dive site.
National Navy UDT-SEAL Museum – Museum of US Navy special forces units
National Oceanic and Atmospheric Administration (NOAA) – US government scientific agency
National Speleological Society Cave Diving Section (NSSCDS) – Organization for exploration, conservation, and study of flooded caves in the US
NATO Submarine Rescue System – Project to develop an international submarine rescue system
Nautical Archaeology Program – Graduate degree program at Texas A&M University
Nautical Archaeology Society (NAS) – British organisation to further research in nautical archaeology for the public benefit
Nautile – Crewed submersible owned by Ifremer
Naval Air Command Sub Aqua Club – British organization within the Royal Navy
Naval diving – Diving in navy applications
Naval Diving Unit (Singapore) – Maritime special forces unit
Naval Service Diving Section – Diving unit of the Irish Naval Service
Naval Special Operations Command – Military unit of the Philippines Navy
Naval Special Warfare Command (Thailand) – Special operations force within the Military of Thailand
Naval Submarine Medical Research Laboratory – U.S. Navy research unit for submarine and diving medicine
Navy diver (disambiguation) – Member of a country's naval forces, specializing in underwater diving
Navy diver (United States Navy) – US Navy personnel qualified in underwater diving and salvage

Ne

Section: Top of section, Na, Ne, Ni, No, Nu

Near miss (safety) , also known as close call – Incident that could have caused harm
Neck dam – Flexible seal between a diving helmet and the diver's neck
Necker Nymph – DeepFlight Merlin class positively-buoyant open-cockpit 3-seater wet sub
Nederlandse Onderwatersport Bond (NOB) – Dutch governing body for underwater sports
Negative buoyancy entry – Scuba diving water entry where the diver will immediately sink
Negative pressure breathing – Breathing gas which is at a slightly lower pressure than in the resting lung
Nemo 33 – Indoor recreational diving facility
Nemrod – Spanish manufacturer of scuba and spearfishing equipment
Neptune Finswimming Club – Club in Bristol, UK.
Nereus (underwater vehicle) – Hybrid remotely operated or autonomous underwater vehicle
Neutral buoyancy – Equilibrium between buoyancy and weight of an immersed object
Neutral Buoyancy Laboratory – NASA astronaut training facility in Houston, Texas
Neutral buoyancy pool – Pool of water in which neutral buoyancy is used to train astronauts
Newtsuit – Atmospheric diving suit designed by Phil Nuytten
New World Publications – Recreational dive guide publisher

Ni

Section: Top of section, Na, Ne, Ni, No, Nu

Night diver – Certification of competence to scuba dive at night
Night diving – Underwater diving during the hours of darkness
Nikonos – Brand of 35mm film amphibious cameras
Nitrogen narcosis – Reversible narcotic effects of respiratory nitrogen at elevated partial pressures
Nitrous oxide (medication) – Gas used as anesthetic and for pain relief
Nitrox – Breathing gas, mixture of nitrogen and oxygen
Nitrox blender – Person competent to blend nitrox for scuba diving
Nitrox diver – Recreational diving qualification to dive using oxygen enriched air
Nitrox production – Methods of producing nitrox mixtures

No

Section: Top of section, Na, Ne, Ni, No, Nu

NOAA Diving Manual – Training and operations manual for scientific diving
No-decompression limit (NDL) – Maximum exposure without incurring decompression obligation
NOGI Awards – Annual awards by Academy of Underwater Arts and Sciences.
No-limits apnea – Freediving discipline in which the diver descends and ascends using their method of choice
Nondestructive testing – Evaluating the properties of a material, component, or system without causing damage
Non-freezing cold injury – Tissue injury due to sustained low temperature without freezing
Nordic Deep – Freediving competition in Lysekil, Sweden
Normocapnia – Normal arterial carbon dioxide levels
Normoxic breathing gas – Mixture with similar oxygen content to air
Normoxic trimix – Breathing gas mixture of helium, nitrogen, and at least 18% oxygen
Normoxic trimix diver – Recreational technical diving certification level
Northern Ireland Federation of Sub-Aqua Clubs – National governing body for recreational diving and underwater sport in Northern Ireland
Norwegian Diver School – Part of the Western Norway University of Applied Sciences
No-stop limit – Diving bottom time beyond which obligatory decompression stops are incurred

Nu

Section: Top of section, Na, Ne, Ni, No, Nu

Nuclear diving – Diving in an environment where there is a risk of exposure to radioactive materials
Nuytco Research – Manufacturer of atmospheric diving suits

Contents: Top	0–9	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z

Index of underwater diving: L–N

Contents

L

La

Le

Li

Lo

Lr

Lu–Ly

M

Ma

Mc–Me

Mi–Mk

Mn–Mo

Ms–Mv

N

Na

Ne

Ni

No

Nu

See also