Underwater search and recovery in the context of "Crewed submersible"

Underwater divers may be employed in any branch of an armed force, including the navy, army, marines, air force and coast guard.Scope of operations includes: search and recovery, search and rescue, hydrographic survey, explosive ordnance disposal, demolition, underwater engineering, salvage, ships husbandry, reconnaissance, infiltration, sabotage, counterifiltration, underwater combat and security.

A submersible is an underwater vehicle which needs to be transported and supported by a larger watercraft or platform. This distinguishes submersibles from submarines, which are self-supporting and capable of prolonged independent operation at sea.

There are many types of submersibles, including both human-occupied vehicles (HOVs) and uncrewed craft, variously known as remotely operated vehicles (ROVs) or unmanned underwater vehicles (UUVs). Submersibles have many uses including oceanography, underwater archaeology, ocean exploration, tourism, equipment maintenance and recovery and underwater videography.

Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave-diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified.

Equipment, procedures, and the requisite skills have been developed to reduce the risk of becoming lost in a flooded cave, and consequently drowning when the breathing gas supply runs out. The equipment aspect largely involves the provision of an adequate breathing gas supply to cover reasonably foreseeable contingencies, redundant dive lights and other safety critical equipment, and the use of a continuous guideline leading the divers back out of the overhead environment. The skills and procedures include effective management of the equipment, and procedures to recover from foreseeable contingencies and emergencies, both by individual divers, and by the teams that dive together.