Equalization, The Most Important Skill in Diving

Why we have to equalize at all

Your middle ear is a small air-filled space sitting behind the eardrum. At the surface the pressure inside it matches the pressure of the air around you, and you never notice it. Descend, and the water pressure outside your body climbs quickly while the air trapped in that space compresses.

If no extra air gets in, the pressure difference starts pulling the eardrum inward. That is the discomfort you feel. Push further and it becomes pain, and past that it becomes injury. Equalizing is nothing more than adding air to the middle ear so it keeps pace with the water outside. It is the reason the descent is possible at all.

The first ten metres matter most

Divers are often surprised to learn that the hardest part of the descent is the shallowest. Pressure doubles between the surface and ten metres, and it never doubles again over any comparable stretch of depth. Between ten and twenty metres you only add half as much again. That is why a diver can fight their ears at three metres and then drop to thirty without another thought once they are through.

So the rule is simple. Equalize early and equalize often. Start on the surface before you leave it, keep clearing every metre or so on the way down, and never wait for your ears to tell you it is time. By then you are already behind.

What happens when you push through it

The first sign is a feeling of pressure or fullness in the ears. Keep descending and it turns into pain. Keep going past that and you risk an ear squeeze, properly called middle ear barotrauma: bleeding behind the eardrum, fluid filling the middle ear, vertigo, temporary hearing loss, and in the worst case a ruptured eardrum. A rupture underwater also floods the middle ear with cold water, which can leave you violently disoriented at depth. That is an emergency in its own right.

Valsalva, the method most divers use

Most scuba divers use the Valsalva manoeuvre whether or not they know its name. You pinch your nose, close your mouth, and blow gently against the pinched nostrils. That pushes air up the Eustachian tubes and into the middle ear, and you feel the small click or squeak of the space opening.

Done gently it is simple and it works. Done aggressively it is a way to hurt yourself, because a hard forced Valsalva can damage the inner ear. Equalizing should feel like a nudge, not an effort. If you are straining, the answer is never to strain harder.

Frenzel, the freediver's method

Freedivers tend to use a different technique called the Frenzel manoeuvre. Instead of using the lungs and chest to push air upward, Frenzel uses the tongue and throat to move a small volume of air into the middle ear. It takes less effort, it keeps working as you get deeper, and it can be done on a descent where the lungs are already compressed.

Plenty of experienced scuba divers learn it eventually, usually the ones who also freedive. It is worth having. For most recreational diving, though, a gentle Valsalva done early and often is all you need.

Reverse blocks, when the air cannot get out

Descending is only half the story. Occasionally air enters the middle ear normally on the way down and then cannot escape on the way up, and the expanding air presses outward instead. That is a reverse block. Congestion, swollen Eustachian tubes, diving with a cold, and decongestant medication wearing off partway through the dive are the usual causes, which is the real argument against diving while you are ill.

It shows up as ear pain during the ascent, a feeling of fullness, and the sense that you cannot keep going up. Never force your way through it. Stop the ascent, give the ears a moment, drop back down a metre or two if you need to, and come up slowly once the pressure clears. Do all of that with an eye on your gas, because a reverse block is a problem you solve patiently rather than quickly. If it does not resolve, end the dive and get it looked at.

The habits that prevent almost all of it

Nearly every equalization problem is solved before it starts, by a handful of habits that cost nothing.

The mistakes that cause the rest

The errors behind most ear injuries are boringly consistent. Waiting until the ears hurt. Descending faster than they can keep up with. Carrying on through discomfort because the group is already going down. Diving congested and hoping it clears. Forcing a hard Valsalva when a gentle one did not work. Ignoring the warning the body gave early and quietly. Good equalization is calm, gentle and frequent, and from the outside it looks like nothing at all.

When to call the dive

If your ears refuse to equalize, the decision is not a difficult one. You do not continue descending. No wreck, no reef and no photograph is worth your hearing, and a dive given up is nothing next to a season given up. The site will still be there tomorrow.

Equalizing is adding air to your middle ear so it keeps up with the water pressure outside. Do it before you feel anything, do it every metre or so, do it gently, and stop descending the moment it stops working. That is the whole skill.

Every experienced diver knows somebody whose diving was cut short by their ears. Sometimes for a day, sometimes for a season, occasionally for good. Equalization is not a hurdle to clear on the way down. It runs the length of the dive, from the surface to the deepest point and all the way back up, and it is the cheapest investment you will ever make in the years of diving still ahead of you.