# Index of underwater diving: L–N

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.
Underwater diving can be described as all of the following:
There are seven sub-indexes, listed here. The tables of content should link between them automatically:
* Index of underwater diving: A–C
* Index of underwater diving: D–E
* Index of underwater diving: F–K
* Index of underwater diving: L–N
* Index of underwater diving: O–R
* Index of underwater diving: S
* Index of underwater diving: T–Z

## 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)
* Monitoring decompression status – Keeping appraised of whether and how much decompression is required by a diver
* Monitoring gas during a dive – Remaining aware of remaining breathing gas quantities
* Monitoring the progress and status of the dive – Underwater diving safety procedure
* 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 |