How does a snorkel work? How to breathe through it and clear it

A snorkel is a short tube that lets you breathe while your face is in the water. One end goes in your mouth. The other end sticks up into the air above your head. You float face down, watch the fish, and breathe the air that comes down the tube.

I teach first-timers to do this every summer on the Adriatic. The tube is never the hard part. The hard part is trusting it.

How does a snorkel work?

A snorkel has three parts:

• A mouthpiece. You hold it with your teeth and seal your lips around it.
• A tube. It runs up the side of your head.
• A clip. It holds the tube to your mask strap.

Your mask covers your eyes and nose. So you breathe only through your mouth, in and out through the tube. As long as the top of the tube is in the air, fresh air comes in with every breath.

Why use one at all? Without a snorkel, you have to lift your head to breathe every few seconds. With one, you can float face down for as long as you like. You save a lot of energy, and you never lose sight of the reef.

Why a snorkel only works at the surface

The top of the tube has to stay above the water. If it goes under, water comes in. A dry snorkel has a valve that shuts the top instead.

So why not make the tube longer? There are two reasons.

• Water squeezes your chest. Just a couple of feet down, the water pushes on your chest harder than your breathing muscles can pull.¹ You could breathe out, but not in.
• Old air stays in the tube. Each time you breathe out, some used air stays in the tube. You breathe it back in first. A normal snorkel holds about 160 to 170 milliliters of it, about two thirds of a cup.² A longer tube would hold more.

That’s why the European safety standard caps an adult snorkel at 38 centimeters, about 15 inches. For smaller lungs, the limit is 35 centimeters.³

So no, you can’t breathe underwater with a snorkel. When you dive down, you hold your breath. To breathe underwater you need a tank of air. That’s the difference between snorkeling and scuba diving.

How to breathe through a snorkel

Start in a pool or in water you can stand in.

1. Try it without the mask first. Put the snorkel in your mouth, close your eyes, and lower your face into the water. Breathe through the snorkel only. This teaches you to leave your nose out of it.⁴
2. Hold the mouthpiece gently. Rest the two tabs between your teeth and bite softly. Seal your lips around it. If you clench, your jaw will ache.
3. Put your mask on and float. Look down and a little forward. The tip of the snorkel should point up over the top of your head.⁵ That keeps it as high out of the water as it can be.
4. Breathe slow and deep. Breathe all the way out, then all the way in. Quick, short breaths just pull the old air in the tube back and forth. That’s what makes people feel out of breath.²
5. Relax and kick gently. Keep your arms at your sides. Let your legs and fins do the work.⁵

If you can’t swim, wear something that floats you. A snorkel vest lets you rest face down without kicking. Read how to snorkel if you can’t swim before your first trip.

How to clear water from a snorkel

Some water will get in. A wave splashes over the top, or you turn your head and dip the tip. That’s normal. There are three ways to get it out.

Blast it out. Blow one hard, sharp puff into the snorkel. The water shoots out the top. If your snorkel has a purge valve, a one-way flap at the bottom, water goes out there too. Then put the tip of your tongue on the roof of your mouth and breathe in slowly. A slow first breath lets you breathe past any drops that are left.⁶

Push it out on the way up. Use this one after you dive down. As you swim back up, tilt your head back and look at the surface. Blow a small puff into the tube as it breaks the water. The air pushes the water out, and you’re ready for your next breath.⁶

Lift your head and dump it. Lift your face, take the mouthpiece out, and let the water run out. It always works.

If you keep getting mouthfuls, read how to snorkel without swallowing water.

The three kinds of snorkel

Type	What it has	Best for
Classic	A plain open tube	Freedivers and spearfishers
Semi-dry	A splash guard on top and a purge valve at the bottom	Most snorkelers, and anyone who dives down
Dry	A float valve that shuts the top when it goes under	First-timers who stay at the surface

A classic snorkel has nothing to go wrong, but every wave gets in. A dry snorkel keeps out almost all the water. It’s bulkier, though, and a wave can shut the valve while you breathe in. If that happens, lift your head and it opens again. If it sticks, take the snorkel out and breathe.

For a first-timer, my pick is a dry or semi-dry snorkel. How a dry snorkel works covers the valve in detail. If you need the whole kit, see which snorkel set to buy.

Diving down on one breath

Once breathing at the surface feels easy, you can dive down for a closer look. Take one or two slow, deep breaths. Hold the last one, and go.

Never take a lot of fast breaths before you dive. That’s called hyperventilating. It makes you feel like you can stay down longer. But it also delays your body’s urge to come up. You can pass out under water with no warning.⁷⁸

Come back up, clear the tube, and rest for a few breaths before the next dive. Always snorkel with a buddy who watches you while you’re down.

Frequently asked questions

How long can you stay underwater when snorkeling?+

Only as long as one breath lasts. The snorkel can't help you once its top is under the water. Come up when you first feel the need to breathe, not later. And never take a lot of fast breaths before you dive to make it last longer.

Can you breathe through your nose while snorkeling?+

Not with a normal mask. Your nose is inside the mask, and the snorkel only reaches your mouth. If you breathe in through your nose, the mask sucks onto your face. Breathe out through your nose only to push water out of a leaky mask.

Is a full-face snorkel mask easier?+

For some people, yes. You breathe through your nose and mouth, like on land, and there's no mouthpiece to bite. But many are made for the surface only. Decathlon says its Easybreath is for seeing and breathing at the surface. Don't dive down in one unless the maker says you can.

What is the point of a snorkel underwater?+

There isn't one while you're under. A snorkel only works with its top in the air. Its job is at the surface. You float face down and watch the reef without lifting your head to breathe. Scuba divers who carry one use it to breathe at the surface without using air from the tank.

Why do I feel out of breath when I snorkel?+

Most often you're breathing too fast. Each breath first pulls back the used air left in the tube, so short breaths get you mostly old air. Breathe all the way out, then slowly all the way in. If you still feel tight, lift your head, take the snorkel out, and rest.

---

Resources

Footnotes

1. “Snorkeling Limits.” Ask the Van, Department of Physics, University of Illinois Urbana-Champaign, 22 Oct. 2007, van.physics.illinois.edu. ↩

2. Toklu, A. S., et al. “Ventilatory and metabolic response to rebreathing the expired air in the snorkel.” International Journal of Sports Medicine 24(3), 2003, PubMed. ↩ ↩²

3. BS EN 1972:2015 Diving equipment. Snorkels. Requirements and test methods. British Standards Institution, 29 Feb. 2016, bsigroup.com. ↩

4. Wilkie, Liz. “Mastering Your Mask Skills.” PADI Blog, Professional Association of Diving Instructors, 29 Nov. 2019, blog.padi.com. ↩

5. Guimbellot, Barry and Ruth. “Snorkeling: Tips for Getting Started.” Dive Training, 4 June 2019, dtmag.com. ↩ ↩²

6. International Training. “Everything You Need to Know About Your Snorkel, Part 3: Clearing Your Snorkel.” Scubaverse, 6 Feb. 2017, scubaverse.com. ↩ ↩²

7. “Travelers Medical Guide 5.5: Water-Related Injuries, Snorkeling and Scuba Diving.” Divers Alert Network, Health and Medicine, accessed 27 Sept. 2026, dan.org. ↩

8. Boyd, C., et al. “Fatal and Nonfatal Drowning Outcomes Related to Dangerous Underwater Breath-Holding Behaviors.” MMWR 64(19), CDC, 22 May 2015, cdc.gov. ↩