Underwater diving is the practice of descending below the water's surface to interact with the environment. Humans are not biologically adapted for deep diving, and must use special equipment to extend the depth and duration of their dives. In ambient pressure diving, with direct exposure to the pressure of the surrounding water, the diver can use breathing apparatus for scuba diving or surface-supplied diving. For repeated deep dives, divers can reduce the risk of decompression sickness by living in a pressurized environment on the surface to prevent pressurization and depressurization as they dive. Atmospheric diving suits may be used to isolate the diver from high ambient pressure. Diving activities are restricted to maximum depths of about 40 metres (130 ft) for recreational scuba diving, 530 metres (1,740 ft) for commercial saturation diving, and 610 metres (2,000 ft) if atmospheric suits are worn. The history of breath-hold diving goes back at least to classical times, and there is evidence of prehistoric hunting and gathering of seafoods that may have involved underwater swimming.

Read more: https://en.wikipedia.org/wiki/Underwater_diving

_______________________________ Today's selected anniversaries:

1862:

American Civil War: The Battle of Perryville, one of the bloodiest battles of the war, was fought in the Chaplin Hills west of Perryville, Kentucky. https://en.wikipedia.org/wiki/Battle_of_Perryville

1897:

Composer Gustav Mahler was appointed the director of the Vienna Court Opera. https://en.wikipedia.org/wiki/Gustav_Mahler

1952:

Three trains collided at Harrow & Wealdstone station in London killing 112 people and injuring 340. https://en.wikipedia.org/wiki/Harrow_and_Wealdstone_rail_crash

1967:

Marxist revolutionary and guerrilla leader Che Guevara was captured near La Higuera, Bolivia. https://en.wikipedia.org/wiki/Che_Guevara

1998:

A new airport for Oslo, Norway, opened at Gardermoen, replacing a smaller one at the same location that had served as a backup to the city's previous main airport at Fornebu. https://en.wikipedia.org/wiki/Oslo_Airport,_Fornebu

_____________________________ Wiktionary's word of the day:

extremity: 1. The most extreme or furthest point of something. 2. An extreme measure. 3. A hand or foot. 4. A limb (“major appendage of a human or animal such as an arm, leg, or wing”). https://en.wiktionary.org/wiki/extremity

___________________________ Wikiquote quote of the day:

Bless the Maker and all His Water. Bless the coming and going of Him, May His passing cleanse the world. May He keep the world for his people.   --Dune https://en.wikiquote.org/wiki/Dune