Glossary of SCUBA Diving - U

U

UHMS

Undersea and Hyperbaric Medical Society

umbilical

Further information: Umbilical cable#Diver

Life support connection to a surface supplied diver or diving bell. Comprises gas supply hoses, a strength member and communications cable, and may also include gas reclaim hose, hot water hose and hoses for hydraulic or pneumatic power, and electrical and optical cables for ancillary equipment. Also refers to the power, control and instrument cable for a ROV.

undertow

A subsurface flow of water returning seaward from shore as result of wave action

upline

also Jersey upline

A fairly substantial natural fibre rope which is deployed from the bottom using a small lift bag to provide the equivalent of a shotline. The lower end is tied off to the bottom, usually on a wreck, and the diver ascends on the line to avoid being swept away from the site by currents. After reaching the surface, the last diver cuts the line and it sinks back down, Natural fibre is used so the line rots away over a few years.

upwelling

An oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water