What is the main function of the 'descent line' during a dive?

The main function of the descent line during a dive is to provide a visual and physical reference for divers as they descend and ascend in the water. This line acts as a guide, allowing divers to maintain a straight and controlled descent or ascent, which is essential for safety and navigation. By following a descent line, divers can better manage their buoyancy and ensure they do not stray from their intended path or depth. Furthermore, the line can help divers keep track of their distance and orientation in the water column, especially in low visibility conditions.

The other options touch on aspects related to diving, but they do not accurately describe the primary role of the descent line. While managing buoyancy is important, the descent line itself does not adjust buoyancy but aids divers in controlling their descent rate. Temperature at depth is monitored through instruments rather than by the descent line, and air consumption is typically tracked with gauge devices rather than being influenced directly by the line. Thus, providing a reference point is the critical and defining purpose of the descent line during a dive.