All of the following are true except:

• A. You can help prevent mask squeeze by exhaling periodically into your mask during ascent.
• B. Regular dental care and ensuring your teeth are free of gas spaces can help prevent tooth squeeze.
• C. If you experience a reverse block, descend to a point where the pain subsides, then ascend slowly while wiggling your jaw and swallowing. Repeat this process as needed until you can ascend without pain or discomfort.
• D. The danger in taking decongestants is that they may wear off during a dive and have other possible side effects.

Answer: (C)

Understanding pressure changes in the ears and face while diving helps you prevent and manage common barotrauma issues. Mask squeeze happens when the air space in your mask is not allowed to equilibrate as ambient pressure changes. Exhaling into the mask during ascent can help keep that air space in balance with the surrounding water pressure, reducing the suction that can press the mask onto your face as you rise.

Tooth squeeze is tied to gas being trapped in teeth or around gas-filled interactions in the mouth. Regular dental care and addressing any gas spaces in teeth reduce the chance of pressure-related tooth pain during dives.

A reverse block is a different challenge that occurs during ascent when the middle ear is not equalizing properly. Safe management emphasizes recognizing when pain cannot be relieved and not forcing the ascent. The approach described—descending to a point where pain subsides and then ascending slowly with jaw movements and swallowing, repeating until you can ascend without pain—suggests repeatedly altering depth to torment the ears and continuing to dive despite unresolved blockage. In practice, if a reverse block cannot be resolved, the safer course is to abort the ascent (or the dive) to prevent ear injury rather than persisting with repeated attempts.

Finally, decongestants can help with congestion but carry risks: they may wear off during a dive and have other side effects, which is why they are not a guaranteed or risk-free aid for equalization.

The statement that doesn’t fit with how reverse-block issues are safely managed is the one describing repeated ascent attempts while the block remains unresolved.