What could a diver's failure to equalize their ears during ascent cause?

Failing to equalize the ears during ascent can lead to a block or reverse block situation. As divers ascend, the pressure decreases, and if they do not equalize the pressure in their middle ear with the external atmospheric pressure, a pressure differential can occur. This differential can cause the eustachian tube, which connects the middle ear to the throat, to become blocked or to function improperly.

In essence, the pressure in the ear may remain higher than the pressure outside, leading to discomfort and pain. If these pressures remain unequal during ascent, the increased pressure on the eardrum can result in severe pain or potential injury to the ear structure. This condition may ultimately lead to a reverse block, where a diver experiences pain and an inability to equalize the ears effectively.

It’s crucial for divers to practice equalization techniques during their ascents to prevent such issues and ensure their safety underwater.