Heliox is a breathing gas mixture used in technical and commercial diving. Heliox is composed of Oxygen and Helium only. Having no Nitrogen it avoid nitrogen narcosis that happens in deeper dives.
To equalize or equalization is the act of applying the same pressure in an air space than the one of the surrounding or ambient pressure. Usually, in diving, it refers to the ears but can also apply to the mask or even to the lungs.
Divers Alert Network or DAN is a non-profit agency that collects and analyze information for divers safety. It has branches that sell different diving oriented services and products such as insurance or oxygen providing kits or First Aid and CPR courses.
Bioluminescence is the ability of some aquatic organisms to generate light. It uses chemical reaction to achieve this. This ability has only been observed in aquatic organisms and only a few terrestrial insects such as the firefly.
fsw or feet of seawater is a measurement unit of the imperial system and represent the pressure in 1 foot of seawater or about 15 psi. 33 feet is also roughly 1 atmosphere.
Mangroves are coastal habitats composed of small trees and bushes that have adapted to the sea water and tides. The roots usually start from just above the surface line at high tide. This makes a vast maze of roots underwater and attracts a very wide biodiversity of marine life. Mangroves play an important role for coasts.
The absolute pressure is compared against a perfect vacuum. It will read the actual surrounding pressure plus the pressure of the atmosphere. It is used in technical or altitude dive planning. The absolute pressure is not the pressure from the submersible pressure gauge as it represents the gauge pressure.