Which condition may occur if a diver ascends too quickly?

Decompression sickness, also known as "the bends," can occur if a diver ascends too quickly after spending time at depths where the pressure is greater than at the surface. When a diver is at depths, their body absorbs more nitrogen due to the increased pressure. This nitrogen is usually released back into the atmosphere during a controlled ascent. If a diver ascends too rapidly, the reduction in pressure happens too quickly for nitrogen to be safely expelled, leading to the formation of nitrogen bubbles in the bloodstream and tissues. These bubbles can cause a range of symptoms, including joint pain, dizziness, and even serious complications affecting the nervous system or lungs.

Understanding this risk is crucial for divers, as it highlights the importance of adhering to safe ascent rates, including making safety stops when necessary. The other conditions listed—nausea, hypothermia, and pneumonia—are not directly related to the rate of ascent during diving, although they can still be serious concerns for divers under different circumstances.