Pressure-Related Diving Issues: Squeezes, Blocks & Safety

How pressure changes affect body air spaces

When you descend in the water, the surrounding pressure increases. A simple way to think about this is Boyle’s law: at a constant temperature, the volume of a gas decreases as pressure increases. Practically, that means any pocket of air inside—or trapped by—your body will compress as you go deeper.

Different air spaces behave differently because of their structure:

• Rigid or poorly expandable spaces: the sinuses and the middle ear sit inside bone and are effectively fixed-volume cavities. They cannot passively change size to match external pressure; they rely on small connecting passages (sinus ostia and the Eustachian tubes) to transmit air to and from the cavity.
• Flexible spaces: the lungs and mask volume are more compliant. The lungs are made of soft tissue and will compress naturally on descent; the mask contains a flexible skirt and a small air volume that will compress unless you add a little air through the nose.

Because rigid spaces can’t shrink freely, they are the ones most likely to cause painful or damaging pressure-related issues in freediving. Flexible spaces usually compress without needing direct equalization, but they have their own considerations—mask equalization and lung compression being the most important for recreational freedivers.

Your body does offer some physiological protections. The mammalian dive reflex redirects blood toward the thorax during immersion, and a “blood shift” around the lung capillaries helps protect delicate alveoli as external pressure increases. Lung tissues also compress rather than tearing under normal breath-hold dives. Those mechanisms are helpful, but they have limits: they do not protect rigid cavities (sinuses, middle ear) that rely on open passages to equalize, and they will not prevent injury if you force equalization excessively or dive while congested or injured.

Common squeezes: ear, sinus, mask and hood

“Squeeze” is the common term for barotrauma caused by an unrelieved pressure difference. The sensation varies by location and severity, from a dull ache to sharp pain and, in severe cases, tissue damage.

Ear squeeze (middle-ear barotrauma)

Cause: failure to ventilate the middle ear through the Eustachian tubes during descent. As external pressure rises, the middle-ear air volume shrinks and the eardrum and middle-ear tissues are pulled inward.

Typical progression: a feeling of fullness progresses to increasing pressure and discomfort. If uncorrected, the negative pressure can draw fluid or blood into the middle ear (making equalization more difficult) and, in severe cases, stretch or perforate the eardrum.

Why equalization matters: the middle ear must be opened periodically to let more air in. If you don’t, the tissue itself bears the brunt of the pressure difference.

Sinus squeeze

Cause: blocked drainage or ostia between a sinus cavity and the nasal cavity (often from congestion, allergies, or inflammation), which prevents trapped air from equalizing as pressure increases.

Symptoms depend on which sinus is involved: frontal sinus pain behind the forehead/eyes, maxillary sinus pain that can feel like a toothache or pain in the cheekbones. Sinus squeezes are painful and can progress if you continue descending.

Mask and hood squeeze

Mask squeeze happens when mask volume is not vented: the internal air compresses and the mask can press on the face and soft tissues around the eyes. It’s uncomfortable and can rupture tiny blood vessels around the eyes.

Hood squeeze occurs when a hood seals too tightly and traps air around the ear canal or outer ear space; the trapped air compresses and interferes with ear equalization. Usually gradual and correctable but can complicate middle-ear equalization if left unaddressed.

Degree of harm ranges from bruising and broken capillaries (which can look dramatic but often heal) to eardrum rupture or more serious middle-ear barotrauma. The good news is that most of these are preventable with attention and early action.

Early warning signs to watch for during a dive

Learning to notice subtle symptoms early keeps dives safe and comfortable. Treat any persistent or worsening symptom as a red flag.

Subtle cues:

• A blocked or “full” feeling in one or both ears.
• A mild, persistent inability to clear the ears with normal equalization attempts.
• Tooth or cheek pain that appears on descent (particularly in one tooth or side).
• Pressure behind the eyes or forehead that doesn’t ease with equalization efforts.
• Mask pressure that feels different than normal—tightness around the eyes or bruise-like feeling.

Sudden signs that indicate serious injury:

• Sharp, intense pain in the ear, sinus, or face.
• Sudden hearing loss, a sensation of blocked hearing that doesn’t clear, or ringing in the ear.
• Vertigo, spinning sensation, or severe imbalance after an ear event.
• Blood or clear fluid draining from the ear (possible eardrum rupture).

If you experience any of these during a dive, stop descending and either ascend slowly or hold your position on the line; do not push through the pain. Persistent or worsening symptoms require immediate cessation of diving and medical evaluation.

Effective equalization techniques and timing

Two main techniques are widely used in freediving: the Frenzel and the Valsalva. For mask equalization you use a different, small-exhalation method. Timing—equalizing early and often—is as important as the technique itself.

Frenzel technique (tongue-piston method)

Why it’s preferred: the Frenzel equalizes by using the tongue and throat muscles to compress the air in the mouth and nasopharynx, so it doesn’t require lung pressure. That makes it very efficient during deep or inverted descents, it uses less air, and it’s gentler on tissues.

Basic steps (practice on land and in shallow water before using at depth):

1. Pinch your nose or close your nostrils internally (small finger position or soft nostril closure).
2. Close the back of your throat by lifting the tongue to the roof of the mouth—think of saying a strong “K” sound or “ng” sound to feel the soft palate seal.
3. Use the back of the tongue to push a small pocket of air from the mouth/nose area into the Eustachian tube openings; you should feel or sometimes hear a subtle pop as the middle ear opens.
4. Release and repeat as needed, especially early in the descent before pressure becomes strong.

Practice until the motion is natural and light—forcing or straining will increase injury risk.

Valsalva basics and limits

Valsalva involves pinching the nose and gently exhaling against blocked nostrils to drive air from the lungs into the middle ear. It’s simple and useful near the surface or during a shallow, head-up descent, but it becomes less effective at depth and when inverted. It consumes more lung volume and can be harder on tissues if overdone.

Mask equalization

Use tiny, controlled exhalations through the nose to add small amounts of air into the mask. A low-volume mask needs far less air to equalize and is a practical choice for freediving. Don’t force big puffs of air—throttle the exhalation by gently pinching your nostrils to let just enough air in.

Timing: pre-equalize at the surface to loosen soft tissues, then equalize early and frequently—well before you feel discomfort. Small, frequent equalizations reduce the force and amount of air needed each time and lower the risk of tissue strain.

Practical prevention: before and during your session

Prevention starts before you step into the water and continues with small choices that become habits.

Health and hydration

• Avoid diving if you are congested, have a recent upper respiratory infection, or have significant allergy symptoms. Open passages are the simplest defense against squeezes.
• Be cautious with decongestants: they may mask symptoms temporarily and can wear off mid-session, leaving you in greater danger. If you are unsure, get medical advice before diving.
• Stay hydrated. Thicker mucus is more likely to obstruct small passages; drink sensibly throughout the day of diving.

Equipment choices and fit

• Choose a small-volume freediving mask to make mask equalization easier.
• Pick a hood that fits comfortably. If your hood creates a tight seal at the ears, learn to break the seal just before the dive so water can enter the hood and trapped air can escape. If you consistently get hood squeeze, adjust the hood or consider one designed with relief ports.
• Ensure your mask skirt sits correctly and your strap is not overly tight—both can affect equalization.

Descent technique

Descend slowly and control your pace with the line. Equalize early and often—don’t wait for symptoms. If equalization becomes hard or painful, stop the descent, hold the line, and either correct the problem or ascend. Never force a painless equalization effort—forcing can cause more damage than stopping.

Practicing with an instructor and structured exercises (such as those available through local courses on manifreediver.ir) helps you build reliable habits and develop the comfort to stop before a problem becomes an injury.

What to do immediately if a squeeze or reverse block happens

Clear, calm actions are the best response.

On descent (squeeze)

• Stop the descent. Hold the line or a fixed point so you won’t sink deeper unintentionally.
• Attempt gentle equalization maneuvers—jaw wiggle, swallow, Frenzel—without force. Sometimes a small change in head position or a gentle neck stretch frees the passage.
• If you cannot equalize comfortably, ascend slowly to decompress the affected cavity and reattempt equalization at a shallower depth or at the surface.
• Do not continue descending through pain; that is the path to tissue damage.

On ascent (reverse block)

• Use the line to slow or stop your ascent so you can try to relieve the trapped air slowly.
• Try jaw movement, swallowing, or gently moving your head and neck. Reverse blocks often occur because the eustachian tube or sinus passage is inflamed and won’t let air escape easily.
• If symptoms persist after surfacing, stop diving for the session and allow the passages time to recover; seek medical advice if anything is unusual.

After suspected barotrauma or eardrum rupture

Surface, stay with your buddy, and seek medical assessment. Avoid flying or further diving until a clinician confirms it is safe. Continuing to dive or exposing a damaged ear to pressure changes can worsen injury and lengthen recovery.

Above all: never continue diving through pain. Pain is the body’s warning system; heeding it prevents larger problems.

Interactions with physiology and other risks

Pressure-related issues do not occur in isolation. Your breathing, medications, hydration, and even stress affect risk.

• Hyperventilation: over-breathing before a dive lowers carbon dioxide and can delay the urge to breathe. This may mask the body’s warning signals and increase blackout risk. It also affects blood flow to the brain and does not protect your ears or sinuses. Avoid excessive hyperventilation.
• Decongestants and medications: they can offer temporary relief, but their effect may wear off during a session and leave you vulnerable. Use them only with medical advice and understand their timing.
• Dehydration and allergies: both thicken mucus and narrow passages, increasing the chance of blockages and squeezes. Manage allergies and hydrate appropriately before diving.
• Pulmonary considerations: lung compression on descent is normal and usually benign in freediving. However, if you suspect lung injury, have respiratory disease, or experience unusual chest symptoms, get medical clearance before returning to depth. Manage buoyancy and ascent profiles to avoid sudden uncontrolled depth changes.

Skills to practice and habit-building for long-term safety

Consistent practice turns good technique into automatic, safe habits.

Dry and pool drills

• Practice the Frenzel on land: get the tongue-piston feeling, practice the soft-palate seal, and learn the minimal pressure that produces the “pop.”
• In shallow water or pool sessions, rehearse mask equalization and small, frequent equalization actions while stationary until the motions are effortless.
• Practice gentle jaw and neck mobility exercises—simple movements that often help free blocked passages.

Buddy routines and pre-dive checks

Develop a clear pre-dive checklist with your buddy: confirm ear and sinus comfort, review equipment fit (mask, hood), agree on the descent rate, and set a clear, shared signal to stop the dive if equalization problems arise. A strong buddy routine normalizes stopping and makes it easier to act early.

Record and review

Keep a simple log of symptoms, near-misses, and what corrected the issue. Patterns emerge: a particular mask, time of day, or allergy season may correlate with problems. Use that record to adjust habits, gear, or to seek targeted coaching.

Pressure-related issues in freediving are common, usually preventable, and manageable with the right habits. Learn to trust early sensations, build reliable equalization skills, and prioritize stopping at the first sign of trouble. Over time these small practices become a routine that protects your ears, sinuses, and enjoyment in the water.