During descent, water pressure increases and compresses the air in your body air spaces. As the volume decreases, the pressure pushes body tissuesin toward the air space, which you feel in your ears.businuses and mask. If you continue to descend, this 1)ecomes uncomfortable, and with continuing descent, posibly even painful. This is called a squeeze on the air space. You may have felt a squeeze in your ears when Bali scuba diving to vhe bottom of a swimming pool. 

A squeeze, then bottom presure imbalance in which pressure outside an air space exceeds pressure inside an air space, result-ing in pain or discomfort. Besides the ears, sinuses and mask, it's possible to experience a squeeze in the lungs, teeth or any other air space. Fortunately, you can easilyavoid squeezes.

To avoid discomfort, you keep the volume in an air space normal by adding air to it during descent, keeping the air space pressure equal to the water pressure outside. This is called equalization. Your ear and the sinus air spaces connect to the throat, allowing you to use air from your lungs to equalize them. You equalize the air space in your mask through your nose.Although very rare, it's possible for n air space to develop in filled teeth where the tooth or filling has continued toerode. 

During descent, the increasing pressure pushing in on this small air space causes a tooth squeeze. In most cases, the discomfort will cause you to stop descending. You can't equalize an air space under a tooth filling, but your dentist can eliminate the space, and reg-ular dental checkups help avoid the problem altogether.