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Snell's window (also called Snell's circle [1] or optical man-hole [2]) is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width of about 96 degrees. [3] This phenomenon is caused by refraction of light entering water, and is governed by Snell's Law. [4]
A diver in a pool wearing an AGA full face mask A diver wearing an Ocean Reef full face mask Head protection helmet for use with Ocean Reef full face diving mask. A full-face diving mask is a type of diving mask that seals the whole of the diver's face from the water and contains a mouthpiece, demand valve or constant flow gas supply that provides the diver with breathing gas. [1]
An aquascope (also called bathyscope) is an underwater viewing device. It is used to view the underwater world often from dry land or a boat. It eliminates the water surface glare and allows viewing as far as water clarity and light permit. The underwater viewer can be used for observing reefs, checking boat moorings, secchi disks and other ...
Scuba diver with bifocal lenses fitted to a mask. Underwater, things are less visible because of lower levels of natural illumination caused by rapid attenuation of light with distance passed through the water. They are also blurred by scattering of light between the object and the viewer, also resulting in lower contrast.
To celebrate World Oceans Day, which takes place on June 8, Google has released a series of new Street View imagery from the world's oceans.
An underwater environment is a environment of, and immersed in, liquid water in a natural or artificial feature (called a body of water), such as an ocean, sea, lake, pond, reservoir, river, canal, or aquifer. Some characteristics of the underwater environment are universal, but many depend on the local situation. [15]
The bird flu outbreak has taken concerning turns, with more than 60 human cases confirmed. Experts outlined four signs that the virus is going in the wrong direction.
A full-face mask may allow the diver to breathe through the nose or mouth as preferred. The demand valve adds a little respiratory dead space to the airway. The work of breathing is greater due to hydrostatic pressure differences between the depth of the demand valve and the lungs, and due to cracking pressure and flow resistance in the demand ...