Scuba Glossary: K - L - M


Kelp Surface Dive  –  A vertical, feet-first, method of descending into water of unknown depth or when obstructions or heavy plant (such as kelp) growth exists; performed by spreading arms and legs, then simultaneously bringing legs together while giving a strong downward stroke with arms thus propelling upper body out of water; body weight will then drive the diver downward; some also find this dive descent easier to equalize ears because there is less blood pressure in head than with pike (head first) dive.

Kilo/kg  –  Kilogram. Metric measure of weight. 1 kg = 2.21 pounds.

Knot  –  The velocity unit of 1 nautical mile (6080.20 ft.) per hour; equivalent to 1.689 ft. per second: to convert ft. per sec. into knots, multiply by 0.592.

K-Valve  –  A simple on and off valve.

Lift Bag  –  After being tied to an object to be lifted, the bag is inflated and will start to rise.

Lift Capacity  –  The amount of buoyancy provided by a Buoyancy Compensator; varies according to size of the BC and according to the purpose of the BC, e.g., a BC intended for use in cold fresh water will provide greater lift capacity than one intended primarily for use in warm salt water.

Live aboard  –  A dive boat with sleeping and eating accommodations. Commercial live aboard boats are usually between 50 and 130 feet long, and can carry from 10 to 30 divers for up to a week or more.

Logbook  –  A diary of a divers dive history. Provides evidence of the depth and breadth of a divers experience.

Low Volume Mask  –  A mask which has a smaller area between the glass and the diver’s face, usually with separate lenses for each eye; requires less air to purge if becomes flooded.

Lubber Line  –  is a fixed line on a compass binnacle or radar plan position indicator display pointing towards the front of the ship or aircraft.


Manifold  –  Used on double cylinder systems. Has 2 valves similar to single tank systems attached by a heavy duty crosspiece with a valve in the center.

Marco Photography  –  A method of getting close-up pictures of a subject by using Marco accessories attached to the camera’s lens.

Mask  –  A skirted glass window constructed to provide air space between eyes and water and to permit both eyes to see in the same plane; a regular mask covers eyes and nose only; modern mask skirts are usually made of silicone rather than the older rubber ones.

Mask squeeze  –  Occurs in rapid descents where the diver neglects to equalize his/her mask. The increase pressure causes tissues around the eyes to swell.

Mask Squeeze  –  A painful condition when the air inside the mask is compressed by the external pressure creating suction on the face and eyes; can be alleviated by exhaling from the nose; can cause permanent eye damage if not equalized.

Mediastinal emphysema  –  Air from an over expanding lung escapes into the center of the chest. This puts pressure on the heart and major blood vessels, interfering with circulation. Symptoms are shortness of breath and feeling faint.

Middle ear  –  Air containing space of the ear bordered on one side by the tympanic membrane, which is exposed to any change in ambient pressure. Air pressure in the middle ear space can only be equalized through the Eustachian tube, which controls the middle ear to the back of the nose.

Mixed gas  –  Any non-air mixture (e.g., nitrox), although some authors use the term only for mixes that contain a gas in addition to (or in place of) nitrogen (e.g., helium).

MOD/ODL  –  Maximum operating depth/oxygen depth limit. The deepest that a diver can safely go using a particular gas mixture. For example, the MOD for EAN32 (32 per- cent oxygen) is 132 fsw (40 m).

Multilevel diving  –  Spending a period of time at several different depth on a single dive.

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