Which of the following is a risk associated with working at depth?

The correct choice highlights a significant risk associated with diving at depth, which is increased nitrogen absorption. When a diver descends, the pressure surrounding them increases, causing nitrogen from the breathing gas to dissolve into the body's tissues at a greater rate. This phenomenon, known as nitrogen narcosis, can lead to a range of effects, including altered mental status, impaired motor function, and increased risk of decompression sickness upon ascent.

Diving at depth means that divers are exposed to higher levels of nitrogen for a longer period, and if they ascend too quickly, the nitrogen can form bubbles in their blood and tissues, leading to serious medical issues. Hence, managing nitrogen exposure and understanding its effects is crucial for safety during deep dives.

The other options present aspects that are less significant risk factors when considering the challenges faced at depth. Increased oxygen availability could actually pose a risk if not properly managed, while decreased buoyancy control and reduced visibility, while relevant, do not highlight the acute physiological risk related to nitrogen absorption that can lead to life-threatening situations.