Flutter kick and mermaid kick: the go-to fin kicks for efficient underwater propulsion

Which kicks are commonly used when swimming with fins?

• A. Side kick and back kick
• B. Butterfly kick and frog kick
• C. Flutter kick and mermaid kick
• D. Crawl kick and dolphin kick

Answer: (C)

The flutter kick and mermaid kick are commonly used when swimming with fins due to their efficiency and effectiveness in propelling a diver through the water. The flutter kick involves alternating leg movements, which provides a smooth and continuous propulsion, making it suitable for divers to maintain speed with minimal effort. It allows for excellent control and direction when underwater. The mermaid kick, on the other hand, combines a streamlined body position with a fluid, wave-like motion of the legs, mimicking the movement of a mermaid's tail. This kick is particularly useful when maneuvering in tight spaces or when extra agility is needed underwater. It generates propulsion while allowing the diver to maintain a streamlined body position, reducing drag. In contrast, the side kick and back kick are less commonly associated with the use of fins, as they are not as effective for forward propulsion and energy conservation. The butterfly kick and frog kick are also not as efficient with fins, since they rely more on undulating motions or sweeping motions of the legs, which don't suit the design of fins. Likewise, the crawl kick and dolphin kick focus more on traditional swim techniques than underwater diving propulsion techniques. This highlights why the selected answer is the most appropriate choice for swimming with fins.

Kicking with fins: what actually gets you moving underwater?

If you’ve ever watched a diver glide through blue water and thought, “What’s turning them that smooth wake?” you’re not alone. The right kicks, paired with fins, can transform how efficiently you move, how long you can stay underwater, and how well you can maneuver around rocks, wrecks, and schools of fish. In IANTD circles (and many other diving programs), two kicks stand out for their mix of propulsion, control, and compatibility with fins: the flutter kick and the mermaid kick. Let’s break down why these two work so well and how you can put them into action.

Flutter kick: the steady engine that keeps you cruising

What it is

The flutter kick is exactly what it sounds like: quick, alternating kicks that resemble a shallow bicycle pedal motion. With fins on, each leg does a light, rapid kick, and the water is pushed backward, creating forward thrust. The motion is continuous, which is why it’s often the go-to when you want a steady pace without fatiguing your hips.

Why it works with fins

• Efficiency through rhythm: Fins add surface area, so a smooth, consistent flutter kick translates to a lot of propulsion with relatively little effort. The secret is keeping your knees flexible and your ankles relaxed so the power travels cleanly through the blade.

• Directional clarity: Because the kicks are small and happen in a steady pattern, you maintain good control over your line. That’s golden when you’re navigating a reef or anchors or want to glide past a passing manta without making a scene.

• Energy conservation: The flutter kick lends itself to longer encounters, especially when you’re hovering while you check your gauges or take a look at something interesting on the sea floor.

How to perform it well

• Body position: Keep a neutral spine, hips level with the surface, and a slight, natural arch in your lower back. Don’t crane your head up or down; look forward or slightly down to keep your aerodynamics clean.

• Leg motion: Engage the quads softly and let the ankles do the work. Picture the blades slicing through the water rather than flailing through it. The kicks should come from the hip joint with the knee staying fairly relaxed.

• Range of motion: Short, brisk kicks are usually more effective than long, stiff ones. If your fin tips are bucking the water, you’re probably overextending.

• Frequency: Start with a comfortable tempo—rapid enough to feel propulsion, slow enough to avoid turning into a tireless engine that burns out mid-mission.

• Common mistakes: Locked knees, tensing up the shoulders, and letting the fins slap the water—these sap your energy and make you feel like you’re dragging a mile of rope behind you.

Mermaid kick: the tail-like motion for tight spaces and agile turns

What it is

The mermaid kick is a graceful, wave-like propulsion technique. Think of the body as a streamlined form with the legs working in a dynamic sweep, almost like a mermaid’s tail gliding through the water. The move is efficient in producing thrust while maintaining a sleek profile, which helps when space is tight or you need quick, agile movement.

Why it works with fins

• streamlined propulsion: The mermaid kick emphasizes a continuous, flowing motion that keeps drag low. Fins amplify this flow, letting you push water backward with a broad, smooth arc rather than a series of choppy, separate motions.

• maneuverability in tight spots: Tight corridors, near coral, or around wreckage demand precision. The mermaid kick makes it easier to pivot, reverse, or slide sideways with controlled speed.

• energy management: Because the motion uses a longer, wave-like stroke, you can cover distance while conserving energy—especially handy for longer underwater routes or when you’re sharing air with a buddy.

How to perform it well

• Body setup: Start with a slightly rounded spine and relaxed shoulders. The goal isn’t a rigid posture but a fluid, efficient line that reduces drag.

• Leg action: The legs flex and extend in a wave from hip to ankle. Your feet stay relaxed, and the fins stay aligned with your legs, tracing a smooth path through the water.

• Timing and rhythm: The mermaid kick blends with a gentle breathing pattern and a steady horizontal glide. You want a rhythm that feels like a natural underwater ballet rather than a sprint.

• Transitions: The mermaid kick shines when you need to shift from forward motion to sidestep or rotate for a better view. Use the tail-like motion to pivot with a minimum drag hit.

• Common mistakes: Over-extending the legs, stiff ankles, or trying to “muscle” the wave. The magic happens when the motion stays loose and focused on a continuous, flowing beat.

Why not some other kicks with fins?

Let’s clear up a quick comparison, because it helps when you’re choosing a technique in the moment.

• Side kick and back kick: Great for certain tasks on the surface or when you’re reorienting in a hurry. But for forward propulsion with fins, they’re not as efficient. They waste energy or pull you off your line rather than helping you glide.

• Butterfly kick and frog kick: Beautiful in pool drills or for specific training, but with fins, they aren’t the go-to choices for propulsion. They tend to disrupt a clean forward path or rely on undulating or sweeping leg actions that don’t pair well with the blade’s geometry.

• Crawl kick and dolphin kick: Classic for human-powered swimming in open water, these can be excellent for training or for surface swims. But they don’t always translate into the most efficient underwater thrust when you’re wearing fins, especially in confined or precise maneuvers.

Real-world nuance: fins, fit, and feel

One small detail often overlooked is fin choice. Short-blade fins can feel snappy and are excellent for rapid maneuvering in reef environments, while long-blade fins deliver power for longer glides, especially in open water currents. The stiffness of the blade also matters: stiffer blades deliver more snap for the flutter kick but can feel harsher on the ankles; softer blades bend more and feel forgiving on longer swims, though they require a slightly different timing to keep up the propulsion.

Fit matters too. A fin that’s too loose or too tight can ruin your rhythm before you know it. Foot pockets that bite into your heel or rub your instep can turn a potentially smooth experience into a distraction. The goal is a secure but comfortable fit that lets your ankles bend naturally and your toes stay relaxed.

Training bites you can take home

You don’t have to go deep into the ocean to get the most out of these kicks. Here are a few practical drills and tips you can slide into your routine, whether you’re on a pool day or practicing in a shallow, clear blue:

• Drills for flutter kick: Do sets of 20 kicks on your back with a buddy watching your hips. The aim is to keep your legs straight-ish with a gentle knee bend, and your toes relaxed. If you notice your hips dropping or your legs toeing in, adjust your kick from the hip and reset.

• Drills for mermaid kick: Practice with a side glide—one arm extended, the other tucked, and the legs moving in a wave pattern. Switch sides to keep symmetry. A towel or small board under your chest helps you feel the line you’re trying to hold.

• Tempo and breath: Pair each kick cycle with a breath. You don’t want to be breathless at the moment you need to steer around a rock. A calm rhythm helps you stay in control.

• Real-world scenarios: Practice finding a line to swim along toward a feature—say a wreck outline or a reef edge—and choose your kick based on the obstacle and distance. In tight corridors, the mermaid kick often wins; in open blue water, the flutter kick can maintain a steady pace with less effort.

A few quick notes on safety and awareness

Kicking with fins isn’t just about speed. It’s about staying aware of your surroundings and the people around you. Fins can be powerful tools, but they can also injure if you’re not careful. Watch your footwork near your buddy, around delicate coral, and when you’re near boats. And if you’re ever unsure about your form, slow down, reset, and reassess.

Pulling it all together: a simple mental map

• When you want consistent propulsion with good efficiency, think flutter kick.

• When you need agile, streamlined motion with the ability to squeeze through tight spots, think mermaid kick.

• Use the right fin for the job, and always keep your body relaxed, your lines clean, and your mind focused on where you want to go next.

• Practice both kicks in a controlled setting before applying them in more challenging environments. The ocean rewards smoothness and restraint just as much as power.

A little analogy to keep it in mind: imagine steering a small boat through a calm inlet. The flutter kick is your steady engine, humming along and guiding you through the current with minimal effort. The mermaid kick is your agile rudder, allowing you to pivot and slip along rock faces or through a narrow channel with grace. You don’t need both at every moment, but knowing when each one shines will make your underwater journeys feel almost effortless.

If you’ve ever watched a diver drift by and wondered how they stay so composed, now you know a core piece of the answer. It’s not about brute force or a single trick; it’s about rhythm, form, and the right tool for the job. Flutter and mermaid kicks aren’t just techniques; they’re a practical way to move through water with confidence, comfort, and a sense of control.

So next time you slip into your suit, lace up your fins, and push off from the safety of the platform, give both kicks a try. Feel the difference, notice where your body and the water click, and let your underwater movements become as natural as breathing. The ocean is patient with you; with the right kicks, you’ll meet it halfway and glide with a little more ease than you thought possible.