Underwater diving

Lore & Background

Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well-adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done. In ambient pressure diving, the diver is directly exposed to the pressure of the surrounding water. The ambient pressure diver may dive on breath-hold (freediving) or use breathing apparatus for scuba diving or surface-supplied diving, and the saturation diving technique reduces the risk of decompression sickness (DCS) after long-duration deep dives. Atmospheric diving suits (ADS) may be used to isolate the diver from high ambient pressure. Crewed submersibles can extend depth range to full ocean depth, and remotely controlled or robotic machines can reduce risk to humans. 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. Technical advances allowing the provision of breathing gas to a diver underwater at ambient pressure are recent, and self-contained breathing systems developed at an accelerated rate following the Second World War.

Reader's Guide

Underwater diving is significant as a human activity that allows interaction with the underwater environment, despite humans not being physiologically adapted to it. The development of equipment such as scuba gear, surface-supplied apparatus, saturation diving techniques, and atmospheric diving suits has greatly extended the depth and duration of dives, enabling recreational, professional, military, and public safety diving. The environment exposes the diver to a wide range of hazards, and though risks are largely controlled by appropriate skills, training, and equipment, it remains a relatively dangerous activity. Professional diving is usually regulated by occupational health and safety legislation, while recreational diving may be entirely unregulated.

Did You Know?

• Immersion in water causes a blood shift from the limbs into the chest cavity and fluid losses known as immersion diuresis.
• The diving reflex is triggered by chilling the face and holding the breath, and is exhibited strongly in aquatic mammals and also exists in humans.
• Cold shock response is a common cause of death from immersion in very cold water, such as by falling through thin ice.
• Blackouts in freediving can occur when the breath is held long enough for metabolic activity to reduce the oxygen partial pressure sufficiently to cause loss of consciousness.