Mask Squeeze

As a diver descends, the ambient water pressure around them increases. For every 10 metres (33 feet) of descent in seawater, the pressure increases by approximately 1 bar (1 atmosphere). This increased pressure compresses the air spaces within the diver's body, including the air trapped inside the diving mask. If this air volume is not replenished, the external water pressure will exert a suction force on the diver's face, drawing soft tissues into the mask.

This suction effect manifests as a 'squeeze' on the eyes and surrounding facial tissues. Early signs include a feeling of pressure or discomfort. If left unaddressed, the blood vessels in the affected areas, particularly around the eyes and on the face, can rupture, leading to visible bruising, red spots (petechiae), or even bleeding in the whites of the eyes (subconjunctival haemorrhage). It's a direct result of Boyle's Law, which states that for a fixed amount of gas at constant temperature, pressure and volume are inversely proportional.

The simplest and most effective way to prevent mask squeeze is to regularly exhale small amounts of air through your nose into your mask during descent. This equalises the pressure inside the mask with the external water pressure, counteracting the vacuum effect. This should be done frequently, similar to equalising your ears, especially during the initial metres of descent where pressure changes are most rapid in proportion to absolute pressure.

Other preventative measures include ensuring your mask straps are not overtightened; the mask should be snug but not constricting. Avoid tight-fitting dry suit hoods or hair that can interfere with the mask skirt's seal, as this can prevent proper equalisation. If you experience discomfort, ascend slightly until the pressure eases, then try to equalise again before continuing your descent. If a squeeze does occur, treatment typically involves rest and allowing the body to naturally reabsorb any blood or bruising; cold compresses can help with swelling.

Liveaboard diving often involves multiple dives each day, sometimes even four or five, making consistent mask equalisation a critical habit. A minor mask squeeze on the first dive can worsen over subsequent dives if not properly managed, potentially leading to persistent discomfort or more severe bruising that could impact your enjoyment of the trip. Establishing a routine of gentle, regular mask equalisation from the very beginning of each descent will ensure your face remains clear and comfortable throughout your liveaboard adventure.

Pay particular attention during deep dives or rapid descents, which are common on liveaboards when exploring specific wreck sites or reef features. Even though the pressure changes are more pronounced in the first 10 metres (33 feet), maintaining awareness throughout the descent is key. If you find your mask is repeatedly squeezing despite equalisation efforts, check the fit of your mask or consider trying a different style if available. Discuss any persistent issues with your dive guide, who can offer advice or alternative solutions, helping you make the most of your Blue Rides experience.

Myth: Mask squeeze only happens in deep water. Fact: Mask squeeze can occur in very shallow water, even just 1-2 metres (3-7 feet) below the surface, because the most significant proportional pressure changes happen in the first few metres of descent.

Myth: A tight mask prevents mask squeeze. Fact: Overtightening your mask straps can actually make mask squeeze worse by preventing the mask skirt from conforming properly to your face and making it harder for exhaled air to enter the mask for equalisation. A snug, comfortable fit is best.

Myth: Mask squeeze is dangerous and requires immediate medical attention. Fact: While uncomfortable and unsightly, most cases of mask squeeze are mild, self-resolving, and not dangerous. Severe cases with significant pain or vision impairment warrant medical evaluation, but minor bruising typically heals on its own.