Glossary of SCUBA Diving - N

N

narcs

Nitrogen narcosis.

Navy SEAL

A US Navy trained combat diver.

neck dam

The lower part of a lightweight diving helmet which includes a neoprene or latex neck seal

NEDU

US Navy Experimental Diving Unit

neo-Haldanian

also neo-Haldanean

Decompression models based on later modifications of the principles described by John Scott Haldane.

Newtsuit

An atmospheric diving suit designed and originally built by Phil Nuytten.

net cutter

A handle with a hooked blade used to cut netting or cordage to free the diver from entanglement

NFCI

Non-freezing cold injuries: Permanent tissue damage due to low temperature exposure without any freezing damage.

niggles

Minor symptoms characteristic of mild decompression sickness.

night diving

Diving during the hours of darkness.

nitrogen narcosis

Also known as narcs, inert gas narcosis, raptures of the deep, Martini effect: A reversible alteration in consciousness that occurs while breathing gases containing nitrogen under elevated partial pressure similar to alcohol intoxication or nitrous oxide inhalation, and can occur during shallow dives, but usually does not become noticeable until greater depths, beyond 30 meters.

nitrox

also Enriched Air Nitrox (EAN)

Mixture of nitrogen and oxygen for use as breathing gas. Usually with oxygen percentage higher than air.

No-mount diving

Further information: Sidemount#Terminology

A specialized overhead-environment strategy for dealing with particularly tight restrictions which may involve divers wearing a very basic harness or simply hand-carrying cylinders.

nystagmus

An oscillation of the eyes alternating a slow eye movement in one direction, and a fast eye movement in the other direction