I've watched hundreds of divers surface early from otherwise perfect dives because of mask squeeze. It's one of those problems that sounds minor until you're 60 feet down with what feels like someone trying to suck your eyeballs out through your forehead. Understanding what is mask squeeze and how to prevent it isn't just comfort stuff—it's fundamental physics that every diver needs to internalize before their first descent.

What Is Mask Squeeze?

Mask squeeze is a pressure-related injury that occurs when the air pressure inside your mask becomes lower than the surrounding water pressure, creating a vacuum effect that literally tries to pull your face into the mask airspace. The technical term is "mask barotrauma," and it happens when you descend without equalizing the air volume in your mask.

Here's the thing: a lot of new divers confuse mask squeeze with mask flooding or poor fit. They're not the same. Mask squeeze is pure physics—Boyle's Law doing its thing. As you descend, increasing water pressure compresses the air inside your mask. If you don't add air to compensate, that smaller air volume creates negative pressure aga…