What is a potential hazard of an uncontrolled ascent?

An uncontrolled ascent during diving poses a significant risk of decompression sickness, often referred to as "the bends." This condition occurs when a diver ascends too quickly from depths where they have been breathing pressurized gas. At greater depths, the body absorbs more nitrogen due to higher pressure. If a diver rises too rapidly, the nitrogen that has been dissolved in their tissues and bloodstream during the dive can form bubbles as the pressure decreases sharply. These bubbles can cause a range of symptoms, affecting the joints, lungs, brain, and even other organs, and in severe cases, can be life-threatening.

Decompression sickness is primarily a concern for divers who do not allow sufficient time for the nitrogen to safely off-gas as they ascend, making controlled ascent practices, including safety stops, crucial in preventing this potentially dangerous condition.