Barotrauma — pressure-related injury

Barotrauma occurs when gas trapped inside your body expands or contracts too quickly. This happens because the surrounding water pressure changes as you move through the water column. Most divers experience this in their middle ear or sinuses during a descent to 10 m. It can also affect your lungs if you hold your breath while ascending. Pain is a clear warning sign. You must equalize your ears every meter since failing to do so causes tissue damage. I saw a student in Koh Tao in 2019 suffer a ruptured eardrum because he ignored ear pain. Never force an equalization if you feel resistance. Always ascend slowly so that the air in your lungs can expand safely without causing a lung squeeze.