Why should divers ascend slowly after deep dives?

Ascending slowly after deep dives is crucial primarily to minimize the risk of gas bubbles forming in the body, which can lead to decompression sickness (DCS). During deep dives, divers breathe compressed air or other gas mixtures at increased pressures, allowing more nitrogen to dissolve into the body's tissues. If a diver ascends too rapidly, the pressure decreases suddenly, causing the dissolved nitrogen to come out of solution too quickly and form bubbles. These bubbles can cause various harmful effects, including joint pain, neurological issues, and even life-threatening conditions.

A controlled, gradual ascent allows the body sufficient time to off-gas the excess nitrogen safely back into the lungs, where it can be exhaled. This process significantly reduces the risk of bubble formation and helps ensure the diver's safety.

The other options, while they might relate to diving in various contexts, do not directly address the primary concern during ascent regarding DCS prevention.