What aspect of diving does the term "umbilical" refer to?

The term "umbilical" primarily refers to the connecting hose for air supply in diving. This hose is a critical component of a diver's equipment, serving as the lifeline that delivers breathable gas from the surface to the diver. The umbilical typically incorporates not just the air supply line, but may also include communication lines and other control mechanisms that allow for safe and effective operations during the dive.

Understanding the function of the umbilical is vital for divers, especially in commercial diving operations, where maintaining a constant air supply is essential for safety and operational efficiency. The umbilical setup allows divers to remain connected to support teams on the surface, ensuring that their air supply and communication systems remain functional throughout the dive.