How Water Works

You're Not Just Swimming - You're Flying Through Water

The Physics Every Swimmer Should Feel

Imagine gliding effortlessly through water, propelled by invisible forces. That's not just a dream for elite swimmers – it's within your reach when you understand the hidden physics at play.

When you swim, you're not just moving your body through water – you're navigating a dense, reactive medium. Water pushes back. It responds. It reveals inefficiencies. And when you start to understand how it works, your swimming transforms.

Swimming Is the Closest We Come to Flying

In water, we float. We glide. We propel ourselves without touching anything solid. In that sense, swimming is the human form of flight – except our medium is denser, heavier, and more resistant than air.

To move through it, we need to generate lift and manage drag, just like a bird or a plane. The difference is that in swimming, every movement of your body affects your speed, balance, and rhythm. You’re not just pushing forward - you’re negotiating a three-dimensional force field of pressure and resistance.

Learning to swim well means learning to fly in a medium that punishes waste and rewards smoothness.

Hydrodynamics – the study of how water behaves around your body – might sound intimidating, but it holds practical, powerful insights for swimmers of every level. You don’t need to be a physicist to apply it. You just need to be curious and willing to observe what the water is telling you.

Let’s break it down.

A Simple Formula That Explains a Lot

At its core, swimming performance boils down to this:

Propulsive Force – Resistance = Acceleration

Propulsive force is the forward momentum you create with your arms and legs. To go faster, you either need to generate more forward force or reduce resistance. Most swimmers focus on the former – more power, more pull, more effort. But smarter swimming starts with the latter: understanding and minimizing drag.

The less resistance you create, the more speed you get from the same amount of effort.

Why Faster Equals More Resistance

There's a fundamental principle every swimmer should know: drag doesn't just increase with your speed, it increases exponentially. This is known as the Theoretical Square Law, and it explains why water feels so much harder to push through at higher speeds.

If you double your speed, your resistance doesn’t just double - it quadruples.

• Swim 1x as fast → drag = 1x

• Swim 2x as fast → drag = 4x

• Swim 3x as fast → drag = 9x

That means the cost of going just a little faster increases dramatically. Even elite swimmers face this wall of water every time they try to accelerate. It’s why swimming “hard” without technical precision often leads to fatigue without faster times.

Key takeaway: To swim faster, especially at higher speeds, reducing drag is often more effective than trying to increase power.

The Three Types of Drag That Slow You Down

Now, let's look at how drag manifests itself in the water, right at your body's surface:

• Form Drag: Think of this as shape-related resistance. If your body is misaligned – head lifted, hips dropped, knees splaying – you’re pushing more water than necessary. A long, narrow body moves faster than a wide, unstreamlined one – just like a sleek jet compared to a bulky cargo plane.

• Wave Drag: Wave drag happens at the surface. As you push forward, you displace water, and it responds with waves. The faster you go, the more waves you make – unless you're streamlined and deep enough to minimize surface disruption.

• Friction Drag: This is the water sliding across your skin or suit. It’s subtle, but at high speeds or over long distances, it matters. This is why elite swimmers shave, and why tight suits help.

Takeaway: Each type of drag compounds. Your job is to streamline your body, calm the surface, and move through the water like you belong there.

Boundary Layers: Where Drag Begins

Right next to your body is a thin layer of water called the boundary layer. It’s essentially water “stuck” to your skin, moving with you. If this layer flows smoothly (laminar flow), you glide. If it becomes turbulent – through splashing, twisting, or breaking posture – drag increases rapidly.

This is why stable, smooth movement matters more than you might think. Erratic limbs or shaky posture disrupt the flow, costing you both speed and energy.

Try this in practice: Swim a few lengths with your eyes closed (in a safe lane). Feel what movements cause turbulence. Which arm feels noisy? Where does water feel chaotic?

How Bubbles Change the Water

Water's density is generally stable. But when you introduce air – via aggressive kicks or a messy hand entry (like a thumb-first splash) – you change that. Air bubbles decrease local density and reduce the water’s “grippiness.”

This matters. Less dense water gives you less to push against. A fluttery, splashy kick creates bubbles that actually reduce how effective the kick is.

The fix: Be intentional with your entries. Clean hands. Quiet feet. Use the water, don’t disrupt it.

Depth and Drag: The Power of Going Under

Wave drag is worst at the surface. But it drops off dramatically when you're just 60 to 100 cm (roughly two to three feet) below the water. This is why elite swimmers stay underwater longer after starts and turns. It’s not just for show - it’s physics.

Even during your stroke cycle, minimizing how much of your body breaks the surface reduces resistance. Think about it in freestyle or butterfly: elbows, shoulders, and knees shooting out of the water may feel strong, but they disrupt flow and increase drag.

Drill: Practice push-offs or dolphin kicks aiming to stay just below the surface. Feel how quiet and fast the water gets.

Why You Stall Mid-Pool

It's a familiar frustration: you start a swim strong, but halfway through the length, you feel like you've hit an invisible wall and your speed tanks. This common mid-pool "stall" isn't usually just fatigue—it's a crucial sign that resistance, or drag, is disrupting your flow.

Drag in swimming isn't something that builds up like lactic acid. It’s always there, acting against you. But its effect can suddenly increase when your technique falters. A dropped elbow, a late breath, or even a slight loss of body tension can change your position in the water and spike resistance. You don’t feel the loss of speed instantly, but within a few strokes, your momentum fades. That’s what we mean by drag "catching up with you."

Think of it like tapping the brakes in a car. One small misstep doesn’t stop you, but it disrupts your rhythm and slows you down. The same is true in the pool. Small technique errors introduce turbulence and disrupt your streamline, costing you precious energy.

This is especially noticeable at moderate efforts, where stability and rhythm matter most. Your goal is to move through the water—not fight it.

Tip: Use Your Warm-Up to Notice Drag

This is your immediate fix. Glide with light effort and pay attention:

• Do you accelerate smoothly, or do you feel resistance stacking up?

• Are your hips riding high or sinking when you breathe?

• Is your catch clean and early, or slipping water?

• Does your stroke feel connected and stable?

Subtle cues like these help you identify where energy is being lost—and where technique can be improved.

Efficiency isn’t just about fitness. It’s about reducing the cost of every stroke.

What to Watch in Your Next Swim

Here’s a simple checklist to take into the pool:

• Splash test: Are you creating more disturbance than necessary? Less splash often means better technique.

• Line check: Is your body long, narrow, and horizontal - or are you folding at the hips and knees?

• Depth awareness: How long do you stay under after a wall? Could you stretch it by even half a meter?

• Feel vs. force: Are you slicing through the water - or pushing against it?

Try picking one of these to focus on per session. Hydrodynamics isn’t about doing more. It’s about doing less wrong.

A Swimmer’s Superpower: Awareness

You don’t need to master physics to improve your swim. But learning to notice what the water is doing around your body - that’s a game changer.

When you start to feel drag instead of just fighting it… When you learn how your shape and splash affect speed… When you get curious instead of just counting laps…

That’s when you stop surviving the length, and start owning it.

Ready to transform your swim from a fight to a fluid dance? In our next issue, we'll translate these physics principles into practical techniques you can apply immediately, diving into how the Swim Mastery method helps you cooperate with water, not brute-force against it. You'll learn to truly connect posture, pressure, and rhythm for a more effortless and powerful swim.