Under which condition is a tending line required for SCUBA divers?

A tending line is essential for SCUBA divers when they are going under any overhead environment. This is primarily because overhead environments, such as wrecks or caves, can restrict the diver's ability to ascend directly to the surface in the event of an emergency. The tending line acts as a safety mechanism, allowing divers to navigate back to the exit point more easily while ensuring that they can ascend safely if needed.

In overhead environments, visibility and orientation can be compromised, making it challenging for divers to maintain their sense of direction or to find their way back to the entrance or exit. The tending line serves as a guide and can prevent divers from becoming disoriented or trapped. This practice enhances safety by providing a reliable way to return to the starting point in potentially hazardous situations.