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Monofin Freediving 101

Last summer, a Mermaid told me the secret of diving with a dolphin’s tail.

"Move as if you want all the creatures in the sea to fall in love with you," she sang in musical siren tones.

With a flash of her tail, she headed for the abyss. Each undulation flowed into the next; her back arched as ripples of pure fun travelled through her body. Her long hair streaming behind her, she wound her way around currents and fish and me in widening arcs of golden skin and cerulean scales. And before I could follow, she was gone.

As you begin your monofin adventure, don’t think of it as a new freediving skill to add to your repertoire. Think of it as pure fun.

And then maybe someone will ask for your phone number.

Two Legs Stuck Together and Nowhere to Go

Anything new requires a move beyond your comfort zone. At first, a monofin can feel clumsy and stupid. But stick with it. The rewards are well worth the goofy-fin stage.

The goal is to learn how to coordinate your entire body into a single swimming muscle. When you do, you will feel like you can move around water somehow, not through it. Learning how to undulate is the secret and joy of monofin freediving.


A good monofin stroke comes from core body flexibility, strength and solid mechanics.

It is hard to undulate with a stiff back, tight hamstrings and poor muscle conditioning.

When you undulate, you should feel your body ripple from just under your clavicle, through your ribcage to your abdomen and lower back, and then to the hips, where the motion is magnified to deliver power to the fin. Your legs and fin are like receptors of a wave, translating the body’s core signal into a propulsive force. If your upper body is stiff-where the undulation is born-the power will be dampened or completely disrupted.

There are many drills to learn the timing of the monofin stroke but it is vital that you do your best to make your body the best possible conduit for the undulation by improving your overall strength and flexibility. Exercises like Yoga and Pilates that use slow dynamic stretches and body-weight exercises are perfect for cross-training. An underwater video camera is also a great tool for evaluating your own stroke. Use one if you can.

The Dry-Land Exercise

Most people have trouble undulating properly. Instead, they use their legs to push themselves forward, pushing down against the water with their feet. A dolphin does not use its tail to swim. The tail anchors the power generated by the dolphin’s core muscles and translates it into speed. Remember that the relative size of a dolphin’s fin is quite small compared to a stock monofin on a human. Dolphins reach incredible speeds with a powerful undulation and active streamlining.

Since the mechanics of the undulation are so important, I devised the following drill to help isolate each muscle and body part involved in the motion.

"The Wall-Worm:"

1. Stand against a wall with your shoulder blades lightly touching the wall, feet shoulder width apart, arms by your sides.

2. Keeping your shoulders still and head looking straight ahead, tilt and lift your chest towards the ceiling.

3. As your spine stretches forward and up, allow your hips and pelvis slide forward-your knees should bend slightly.

4. Let your chest tilt downward and fall back toward the neutral position.

5. Engage your stomach muscles to bring your chest down slightly and bring your hips back.

6. Allow your legs to straighten, as your hips, spine and chest all return to the starting position.

The amplitude of this undulation should be small – all within three or four inches. Your shoulder blades should stay fairly close to the wall. If they bang against it, you are probably bending too much at the waist. Your shoulder blades and head should be still.

This drill represents the basic form you should have when ascending from a dive. A descent would use a slightly greater amplitude. Notice how your legs barely move and bend slightly at the biggest part of the motion.

Once you feel a good undulation, link together each step to make a fluid motion. Pretend it’s a new dance craze and invite all your friends over! Practice this often, at the office, before bed, on the beach before you go in the water-focus on the rippling sensation.

Your New Best Friend

Chose your monofin as you would choose a pair of running shoes. The perfect monofin gives you a snug fit for power transfer and just enough room for blood circulation. The footpocket must be stiff enough to prevent the force of the undulation from bending your foot instead of the fin.

A Fiberglas monofin is recommended for starting out. With your hand you should be able to bend the fin’s edge ninety degrees toward the footpocket with ease. Stiffer fins-used for finswimming sprints-require better conditioning, a higher undulation frequency and not suitable for the slower pace of freediving.

Spend time to put your fin on properly. Wear neoprene sock to prevent chafing. Lubricant helps slide your foot deep into the footpocket for optimal control.

Swimming Out to Sea

Imagine you are a shark. Turn on your side, extend your lower arm above your head and let your surface arm trail by your hip. Now you can cheat a little and let your lead arm sweep from side to side to initiate the undulation. Let your body follow through like a whip. Hold your snorkel in your surface hand and breathe to the side in mid-stroke. The side-stroke is a relaxing way to swim on the surface. Long surface swims are a great way to build your monofinning muscles.

In the Water at Last

The easiest and most natural undulation is coming up from a dive. The body is balanced, the lungs are full and pull you toward the surface. And it is always easier to concentrate on a new skill when you are heading towards air.

Find shallow water no more than 20m deep and drop a depth line down that is highly visible to you underwater. Putting a marker at -10m and -15m is a good idea. With a buddy to supervise and offer feedback, you can teach yourself a monofin stroke that even Mermaids will admire. The shallow depth allows you to dive in a relaxed state of mind and concentrate fully on each technique.

For each of the drills below, pull yourself down the line to -10m or -15m below the surface-whatever is most comfortable-turn around and undulate back to the surface with your arms by your sides.

Repeat this simple drill several times, and then when it feels good, try these ascent drill variations:

1. Keep the head still and look directly at the line. Your line of sight should be perpendicular with the vertical line.

2. Concentrate on doing the Dry-Land drill on the ascent. Focus on your chest, back and abdominals. Are they powering the undulation? String together each step in a smooth motion.

3. Alternate between undulating with your core muscles and moving only by kicking with your legs. Feel the difference. Switch back and forth. This drill helps further isolate the critical muscles for a smooth stroke.

4. Sprint on the ascent without using leg power. You should feel your abdominal and back muscles work. Stop and correct if you notice you are using your leg muscles.

5. Undulate with arms overhead. Not rigid like a competitive swimmer, but relaxed. Keep your head still and feel your body ripple like a sea snake.

Between each dive focus on how the undulation felt and try to visualize how you can improve it on the next attempt. Give each drill variation at least five repetitions before moving on to the next. Over several months, these exercises will improve your technique. When you feel it "click," focus on the drill and try to recapture the sensation on every subsequent drill.

The Descent

A graceful monofin stroke equals excellent technique. Unfortunately, many novices start off by thrashing and flailing to get underwater. Whales are the best example to follow: Watch a humpback ease itself beneath the surface.

The descent can be broken into a few simple steps:

1. Take your last breath, pike the body from the waist, raise the legs, allow your body weight to drive the fin below the surface.

2. Make one or two sculls with the hands and equalize if necessary between each scull.

3. Build your downward momentum with a few strong and wide undulations. Use your quads is necessary for an extra boost to overcome high buoyancy (for all you winter freedivers).

It’s good to practice these steps on every dive. Ask your buddy to watch from the surface and give you feedback.

Staying vertical on the descent is a challenge because the buoyancy of the lungs destabilizes the body. Concentrate on looking directly at the line. Looking down will throw off the undulation, increase drag and make it more likely that you will descend on an angle. Use your hands to adjust your trim and if you get really messed up, grab the line to correct your path. The more practice with descents, the better.

Navigating the Bottom.

The monofin is a dangerous weapon when attached to a careless diver. The blade can leave gashes in a reef, stir up silt, and slice the skin of a fellow diver.

Use your hands to pull yourself along the bottom and scull with your hands to keep a good metre or two between yourself and your launch pad should you decide to return to the surface.

The Ascent

After doing so many ascent drills, this part should be automatic. Remember that a good stroke works the core muscles. If you ascend under leg power, it will seem as though you are flicking at the water with little apparent effect in speed and momentum. And then your legs will quickly burn with lactic acid.

Troubleshooting Common Problems

"I undulate my body but I don’t go anywhere."

Causes: Undulation stalls in upper body, poor follow-through to hips, legs and fin.

Cure: Make huge amplitude undulations, over-exaggerate every stroke. Imagine your body slipping over an imaginary hill. Curve your back and hips over the hill and then arch your body on the other side to drive power to your fin. You should feel a rush of speed.

"My head moves around and my neck is sore after diving."

Causes: Stiff back, bending at the waist, head not in neutral position, using legs to kick, poor undulation.

Cure: Proper stretching before diving, practice dry-land drills and ascent drills, keep head in neutral position.

"My buddy says my stroke looks awkward."

Cause: Fatigue, lack of flexibility, timing is off.

Cure: Return to simple drills and dry-land exercise. Rest.

"I corkscrew and drift away from the line on the way down."

Cause: Uneven leg and foot pressure. (Or one leg is longer than the other!)

Cure: Try following drill: Pull down line with hand, keeping the line almost against your mask. Make three undulations and concentrate on maintaining even foot pressure. Correct your position if necessary, pull on line again, try undulations again. Repeat on ascent. Using your core muscles will minimize this problem. Kicking will make it worse.

Mermaid Safety

Freediving with a monofin brings up some special safety considerations. Adept monofinners find ascending from depth to be much easier than with bi-fins. It is also much easier to generate power to lift a person to the surface. But dexterity and balance underwater and on the surface are a little more challenging.

For these reasons, underwater rescues for blackouts and other hazards should be practiced with a monofin. You should familiar yourself with the modifications necessary to make effective rescues.

The traditional underwater assist to bring a freediver in trouble to the surface requires a tight undulation so that you don’t bump him with your body. Helping the victim on the surface also requires practice. Whereas with bi-fins you would sit straight up in the water and attend to the diver, a monofin freediver has to lean back slightly and let his upper body buoyancy keep him stable and above water to assist the victim.

A trio of freedivers should be the minimum for any kind of depth training. One diver, one spotter and a surface spotter to assist if needed. A surface spotter in bi-fins is an added safety precaution.

Final Remarks.

Developing a good monofin stroke does take time and patience. Luckily for you, practice is fun and the benefits to your fitness are considerable. Only monofin training can give you a "twelve-pack."

And best of all, when diving with a monofin, you feel like a mythical creature. You feel sleek like a seal, powerful like an Orca, dangerous like a shark, playful like a dolphin, and-if you’re lucky-you might lure a human of your own to the depths of the ocean.

Good luck!

Monofin Extra!

Monofins for Sale

Sebak Fins

Mat-Mas Italia

WaterWay Company

Finis USA

Essential Accesssories

Neoprene socks

Depth Line


Depth gauge

Peter Scott
Peter Scott
Peter Scott freedives in British Columbia, Canada. After competing in the World Championships for Canada in 2001, he has continued his exploration of the ocean through writing, art, photography, freediving, swimming, surfing, windsurfing, and travel. Visit his website at