Submersible

The vehicle had small glass windows on top and naturally luminescent wood[clarification needed] affixed to its instruments so that they could be read in the dark.

[citation needed] Bushnell's Turtle was first set into action on September 7, 1776, at New York Harbor to attack the British flagship HMS Eagle.

Lee successfully brought Turtle against the underside of Eagle's hull but failed to attach the charge because of the strong water currents.

[citation needed] Some submersibles operate on a "tether" or "umbilical", remaining connected to a tender (a submarine, surface vessel or platform).

A third technology is the "wet sub", which refers to a vehicle that may or may not be enclosed, but in either case, water floods the interior, so underwater breathing equipment is used by the crew.

During underwater operation a submersible will generally be neutrally buoyant, but may use positive or negative buoyancy to facilitate vertical motion.

Some submersibles use high density external ballast which may be released at depth in an emergency to make the vessel sufficiently buoyant to float back to the surface even if all power is lost, or to travel faster vertically.

The bathyscaphe Trieste was the first to reach the deepest part of the ocean, nearly 11 km (36,000 ft) below the surface, at the bottom of the Mariana Trench in 1960.

[citation needed] China, with its Jiaolong project in 2002, was the fifth country to send a person 3,500 meters below sea level, following the US, France, Russia and Japan.

On June 22, 2012, the Jiaolong submersible set a deep-diving record for state-owned vessels when the three-person sub descended 6,963 meters (22,844 ft) into the Pacific Ocean.

[7] Among the most well-known and longest-in-operation submersibles is the deep-submergence research vessel DSV Alvin, which takes 3 people to depths of up to 4,500 metres (14,800 ft).

[8] James Cameron made a record-setting, crewed submersible dive to the bottom of Challenger Deep, the deepest known point of the Mariana Trench on March 26, 2012.

Limiting Factor was commissioned by Victor Vescovo for $37 million and operated by his marine research organization, Caladan Oceanic, between 2018-2022.

SEAmagine Hydrospace, Sub Aviator Systems (or 'SAS'), and Netherlands-based U-boat Worx have developed small submersibles for tourism, exploration and adventure travel.

A Canadian company in British Columbia called Sportsub has been building personal recreational submersibles since 1986 with open-floor designs (partially flooded cockpits).

Remotely operated vehicles (ROVs) repair offshore oil platforms and attach cables to sunken ships to hoist them.