The middle ear is an air-filled cavity behind the eardrum. On descent, water pressure pushes the eardrum inward unless you actively push air through the Eustachian tube to balance it. If you can't, it hurts, and below a few metres of pressure differential the eardrum can rupture. The single biggest fix is starting earlier and going slower. Equalise on the surface, equalise before you feel anything, equalise every metre. Don't wait until you feel pressure. If you have recurrent problems after technique work, see an ENT — there are real anatomical causes that need diagnosis.
The physiology in two paragraphs
Your middle ear is a small air-filled chamber behind the eardrum. It connects to the back of your throat through the Eustachian tube — a narrow passage that normally stays closed and only opens when you swallow, yawn, or actively push air through it. The Eustachian tube’s job is to equalise air pressure between the middle ear and the outside world.
When you descend in water, ambient pressure rises fast. At 10 metres, you’re at 2 atmospheres absolute — double the pressure at the surface. The water pushes the eardrum inward. To restore balance, you need air on the inside of the eardrum at the same pressure as the water outside. The only way to get it there is through the Eustachian tube. If the tube doesn’t open, the eardrum stays bowed in, the pressure differential keeps growing, and you experience increasing pain. At around half a metre of unequalised descent, fluid and blood can be pulled into the middle ear (middle ear squeeze). At a couple of metres without equalisation, the eardrum can rupture.
The ascent has the opposite problem in theory but usually equalises passively — gas expanding in the middle ear simply leaks out through the Eustachian tube on its own. Usually. Reverse blocks (when it doesn’t) are a real but uncommon issue and we’ll get to them.
Why new divers struggle
The most common mistakes, in rough order of frequency:
Equalising too late. Waiting until you feel pressure. By the time you feel it, the Eustachian tube is already partly collapsed by the inward pressure on it, and forcing it open requires much higher pressure than if you’d cleared it earlier. The fix is the rule every instructor repeats: equalise on the surface, equalise as you start descending, equalise every metre for the first 10 metres.
Going down too fast. Most descent problems are pace problems. New divers tend to descend faster than they can equalise. The fix is to take the descent in 30-second increments. There is no prize for being first to the bottom.
Dehydration. The Eustachian tube lining works better when you’re well hydrated. Long-haul flights, hot tropical destinations, alcohol the night before, and skipped breakfast all reduce equalisation capability noticeably.
Mild congestion. A cold you think is “just clearing up” can be enough to block the Eustachian tube. Recent flu, recent allergies, recent sinus infection — all relevant.
Holding the nose too tight or too loose. The standard Valsalva technique relies on a sealed nose. New divers sometimes seal too tight (squeezing the nostrils against each other rather than against the septum), or not enough.
The four equalisation techniques
Most instructors teach Valsalva first because it’s intuitive. The other three are worth learning if Valsalva isn’t working for you.
Valsalva
Pinch your nose closed. Gently blow against the closed nose. The pressure pushes air up through the Eustachian tube into the middle ear.
When it works. Most healthy divers, most of the time. Easy to teach, easy to do.
Limitations. Valsalva is a passive technique that depends on the Eustachian tube being relatively easy to open. If your tube is reluctant — congestion, anatomy, fatigue — Valsalva won’t be enough and harder forcing will only inflame the tissues and make the problem worse. Never force a Valsalva.
Toynbee
Pinch your nose closed and swallow. The swallow action opens the Eustachian tube briefly. The closed nose creates a small pressure differential that pushes air into the middle ear.
When it works. As a complement to Valsalva on descent, or as the primary technique for divers whose Eustachian tubes don’t respond to Valsalva.
Limitations. Less reliable than a good Valsalva for many people, but works better for some.
Frenzel
Pinch your nose, close the back of your throat (the same closure you use to lift something heavy), and use your tongue as a piston to push air into the middle ear from the back of the throat.
When it works. Frenzel is the technique freedivers use because it’s gentler, can be done repeatedly without strain, and works on a partial breath. Many recreational scuba divers don’t learn it but it’s the most useful technique for anyone with finicky ears.
Limitations. Harder to learn. Takes practice. Best taught by someone who already does it.
Edmonds technique
Tilt the head to one side, with the ear you’re equalising upward. Then perform a Valsalva or Frenzel. The neck tilt physically opens the Eustachian tube on the upper side, making it easier to equalise.
When it works. When one ear is harder to equalise than the other. Common — most divers have a “weak” side.
Pre-dive checklist to prevent problems
The night before:
- No dairy if you find dairy causes mucus for you (varies by person)
- No alcohol — alcohol dehydrates the Eustachian tube lining and tends to cause swelling
- Hydrate properly
The morning of:
- Drink water, not just coffee
- No recent strenuous workout that left you congested
- Practice three to five Valsalvas before you leave for the boat — feel them work, feel the click
On the boat:
- Equalise on the surface before you even start descending
- Equalise as your face touches the water
- Equalise every breath for the first 5 metres
- Slow your descent. If your buddy is pulling away, signal them and equalise
What to do underwater if you can’t equalise
The rule is simple and worth memorising: stop, ascend slightly, try again.
If you feel pressure or pain, do not push harder. Do not “see if it sorts itself.” Both of those make the problem worse — the eardrum is already bowed in and forcing it harder pulls fluid into the middle ear.
Instead:
- Stop your descent immediately. Signal your buddy.
- Ascend half a metre to a metre.
- Try Valsalva again, gently. If it works, you’re equalised — wait a moment, then continue descending slowly.
- If it doesn’t work, try Toynbee or Frenzel.
- If you still can’t equalise, the dive is over for that ear. Signal your buddy and ascend with them.
There is no shame in calling a dive. Every experienced diver has done it. The alternative is a ruptured eardrum, which means a week off diving and possibly an ENT visit.
Reverse blocks — the ascent problem
A reverse block is when gas in the middle ear or sinuses can’t escape on the way up. As you ascend, that gas expands, and if it can’t find a way out it creates internal pressure that pushes the eardrum outward.
Reverse blocks are uncommon but worth knowing about. Causes:
- A decongestant taken before the dive that wore off during the dive (the Eustachian tube reopens for descent but is swollen shut for ascent)
- A developing sinus infection that wasn’t apparent before the dive
- Anatomical narrow Eustachian tube that lets air in but not out
If you feel pressure building in your ear on ascent, the response is the same as descent equalisation in reverse: stop, descend half a metre to reduce the gas volume, try gentle equalisation manoeuvres, then ascend slowly. Most reverse blocks clear within a minute or two.
The reason decongestants are not generally recommended for diving is precisely this reverse-block risk. A decongestant that wears off mid-dive can turn a manageable descent problem into a more serious ascent problem.
When to abort a dive
Any of these should end the dive immediately:
- Persistent ear pain after stopping and trying to equalise
- Vertigo — the sense that the world is spinning, often caused by water entering the middle ear through a ruptured eardrum
- Sudden hearing change underwater
- Discharge or fluid from the ear
Underwater vertigo is particularly dangerous because you lose orientation. If it happens, signal your buddy, hold onto them or a fixed object, and ascend with their help.
When to see an ENT
Some equalisation problems are not technique problems. They’re anatomy or medical problems. See an ENT (preferably one with dive-medical familiarity — DAN’s directories can help) if you experience any of:
- Recurring inability to equalise across multiple dive trips, despite good technique
- Hearing loss persisting after diving
- Vertigo continuing after the dive
- Blood from the ear, even a small amount
- Fluid or feeling of fullness in the ear lasting more than 24 hours after diving
- Recurrent ear infections
- Tinnitus (ringing) that started after a dive
Conditions an ENT might find:
| Condition | What it is | What it means for diving |
|---|---|---|
| Eustachian tube dysfunction | Narrow or sluggish Eustachian tubes | May be improvable with treatment, sometimes balloon dilation |
| Deviated septum | Cartilage misaligned in the nose | Can complicate Valsalva, sometimes surgically corrected |
| Chronic sinusitis | Persistent inflammation in the sinuses | Treat the sinusitis first, then re-evaluate diving |
| Cholesteatoma | Abnormal skin growth in the middle ear | Usually needs surgery, dive clearance after recovery |
| Perforated eardrum (recent) | Hole in the eardrum from previous trauma | No diving until fully healed, ENT verification |
| Otitis externa | Outer ear canal infection (swimmer’s ear) | Treat first, dive after clearance |
| Patulous Eustachian tube | Tube stuck open instead of stuck closed | Less common, can cause its own diving issues |
The standard considerations for each of these vary widely. Talk to a dive-trained ENT for clearance decisions — DAN’s referral directories at daneurope.org and diversalertnetwork.org list physicians with dive-medicine familiarity globally.
Don’t dive with a cold
This is the most-repeated piece of practical advice and the most-often-ignored. A cold means swollen Eustachian tubes and inflamed sinuses. The combination dramatically increases the risk of:
- Inability to equalise on descent (causing barotrauma)
- Reverse blocks on ascent (worse, because the dive is already over and you’re trying to surface)
- Sinus squeeze (sinuses don’t equalise as easily as the middle ear)
The temptation to dose up on Sudafed and dive anyway is strong on a holiday where you’ve paid for the course. Resist it. The reverse-block risk in the second half of a dive when the decongestant wears off is the specific worry, and “I felt fine on the first dive” does not mean “I’ll feel fine on the third.”
If you’re sick at the start of a multi-day course, talk to the instructor on day one. Most shops will let you reschedule confined-water sessions or extend the course by a day or two. The financial pain of an extra day on the island is much smaller than the pain of a ruptured eardrum on day three.
Train your ears before the trip
Two weeks before your dive course, start practising:
- Three to five gentle Valsalvas a day, on dry land, in the shower
- Get familiar with the click sensation when both ears equalise
- Try Toynbee while sipping water — feel the difference between a swallow with sealed nose and one without
- If one ear is consistently harder, work on the Edmonds head-tilt for that side
This is the dive-doctor equivalent of “do some cardio before your ski trip.” Two weeks of awareness pays off enormously on day one of the course.
For divers with persistent issues, the Otovent balloon is a small inflatable balloon you inflate through your nose. Used twice a day for two to three weeks before a trip, it conditions the Eustachian tubes. Available over the counter in most European pharmacies. Discuss with an ENT or dive doctor before you rely on it.
Ready to book?
We compare Koh Tao dive shops on instructor experience and how they handle students with equalisation issues. Some shops are noticeably better at slowing the descent and giving students time to learn the technique. The shop matters.