A diver blowing against a pinched nose might risk:

When a diver blows against a pinched nose, they are trying to equalize the pressure in their ears, specifically the Eustachian tubes. However, if this action is performed improperly or with too much force, there is a risk of causing a rupture in the round window membrane of the inner ear.

The round window, located in the cochlea, plays a critical role in hearing and pressure regulation within the inner ear. If it ruptures, it can lead to significant complications, including hearing loss or balance issues. This risk emphasizes the importance of using proper equalization techniques and understanding the pressures involved during diving, as excessive force can result in serious injury.

Understanding this risk is crucial for divers as it highlights the need for careful equalization practices to avoid harm to the delicate structures of the ear during ascents and descents.