What is the most likely cause of vertigo experienced during descent?

The most likely cause of vertigo experienced during descent is a perforated eardrum. As divers descend, they encounter increasing water pressure, which affects the pressure in the middle ear. If there is a perforation in the eardrum, it can disrupt the normal equalization of pressure in the ear, leading to an imbalance. This imbalance can result in disturbances of the vestibular system, which is responsible for balance and spatial orientation, thereby causing sensations of vertigo.

In addition, a perforated eardrum might also allow water to enter the middle ear, further complicating equilibrium and leading to additional symptoms. It’s crucial for divers to equalize their ears properly during ascent and descent to prevent such conditions and ensure equal pressure, thus avoiding vertigo.