The correct answer is option 3 - high water pressure.

When a deep-sea diver dives into the ocean, the pressure of the water increases with depth. This increase in pressure, known as water pressure, can have a harmful effect on the body.

One of the vulnerable parts of the body is the ear. The ear consists of a small air-filled chamber called the middle ear, which is separated from the external environment by the eardrum. The eardrum is a thin membrane that vibrates in response to sound waves, allowing us to hear.

The high water pressure, especially at greater depths, can exert a significant force on the eardrum. This force can cause the eardrum to rupture or burst, leading to pain, hearing loss, and other ear-related problems. This condition is known as barotrauma.

The other options, lack of oxygen (option 1) and high atmospheric pressure (option 2), also have their own risks and complications in diving. However, in the context of the question, the primary reason for the potential harm to the ear drum is the high water pressure.