What is a critical factor divers must monitor to avoid decompression sickness?

Monitoring depth is crucial for divers to avoid decompression sickness, commonly known as "the bends." Decompression sickness occurs when a diver ascends too quickly after spending time at significant depths. As a diver descends, the pressure increases, causing more nitrogen to be absorbed by the body tissues. If a diver ascends rapidly, the dissolved nitrogen can form bubbles in the bloodstream and tissues, leading to potentially serious health complications.

By closely monitoring and controlling their depth, divers can plan their ascent and include safety stops, allowing the body to eliminate excess nitrogen gradually and safely. Managing depth is instrumental in following safe diving practices and adhering to dive tables or dive computers, which provide guidelines for safe ascent rates based on the diver's time spent underwater and the depths reached.

While factors like temperature, air pressure, and visibility are important for overall diving safety and comfort, they do not directly influence the mechanics of decompression sickness in the same critical way that depth does.