How the official rules don’t just define what’s legal — they actually build a faster, more efficient Butterfly stroke.
By Abbie Fish — Founder, Swim Like a Fish | Coach, Clinician & Stroke Specialist
What if your Butterfly technique doesn’t feel smooth because you’re fighting the rules — not using them?
Most swimmers learn Butterfly by copying what they see. They watch elite swimmers, try to mimic the movement, and hope it eventually clicks. But without understanding the Butterfly rules, you’re guessing your way through one of the most technical strokes in the sport. And Butterfly does not reward guessing.
Every part of the stroke — your timing, your rhythm, even how your body moves through the water — is directly shaped by the rules. Once you understand that, Butterfly stops feeling like a fight and starts feeling like a system.
Before diving into each rule, here’s the full model. Every legal Butterfly stroke follows the same sequence:
This is the pipeline. Each rule defines how one piece connects to the next. Miss one and the whole system breaks down.
Swimmers often think of rules as something you “check” during a race so you don’t get disqualified. But in Butterfly, the rules are much deeper than that—they actually define what efficient movement looks like.
Take the requirement that both arms move simultaneously. That’s not just about fairness. It forces the swimmer into a symmetrical pattern that maximizes propulsion. The same goes for the dolphin kick. You can’t alternate your legs, not because it’s unfair, but because it breaks the rhythm.
It also reduces forward momentum.
USA Swimming Rule 101.3.2 “Both arms must be brought forward over the water and pulled back simultaneously. From the beginning of the first arm pull, the body shall be kept on the breast.”
So when swimmers struggle with Butterfly, it’s rarely because they’re not trying hard enough. It’s usually because their technique is fighting the structure that the rules are trying to enforce.
According to USA Swimming rule 101.3.2 and FINA rule SW 8.5, Butterfly starts with a forward start. The underwater phase may extend up to 15 metres (16.4 yards). On paper, that sounds simple. In reality, this is one of the most misunderstood — and most wasted — phases in the entire stroke.
FINA Rule SW 8.5 “It shall be permissible for a swimmer to be completely submerged for a distance of not more than 15 metres after the start and after each turn. By that point, the head must have broken the surface.”
Most swimmers rush this phase. They dive in, take a few dolphin kicks, and pop to the surface as soon as possible. But if you watch elite swimmers, you’ll notice something very different. They stay underwater longer, keep a tight streamline, and use strong, controlled dolphin kicks to build speed before they take a stroke.
This works because water resistance is lower when you’re fully submerged and aligned. The moment you break the surface, drag increases. The rule that allows 15 meters underwater isn’t just a limit — it’s an opportunity.
But staying underwater long enough is only half the equation. How you resurface matters just as much. One of the most common breakout mistakes is linking only the first dolphin kick to the breakout stroke.
This can happen even for experienced swimmers. They then skip the second kick. It feels like an energy-saving shortcut, but it actually kills the momentum you just spent 15 meters building. Both kicks need to fire on that initial stroke to surge you cleanly through the surface. If you’re not sure whether you’re doing this, get someone to film you underwater. Video review makes the difference immediately visible in a way that poolside coaching alone cannot.
Technique Takeaway Don’t rush to swim. Build speed first, then transition to the surface with control. Use the full 15 meters as a strategic advantage — and make sure both kicks connect on your breakout stroke, not just the first one.
The main change is this: the video’s key insight about the two-kick breakout is now part of the main text. It reads like a natural teaching point, not an afterthought below the section. The takeaway box was updated to reflect it too. The transition from the rule/physics argument into the practical coaching detail flows as one continuous thought.
One of the key Butterfly Rules — in both USA Swimming (101.3.2) and FINA (SW 8.1) — states that the body must remain on the breast. At first glance this seems obvious, but it has major implications for how the stroke should feel.
Butterfly is not totally flat and it is not rigid. It’s a wave — called Undulation — that travels from the chest through the hips and into the kick. Every elite butterflier in history has undulated. There are no exceptions.
The movement happens around the hips. Chest presses down, hips follow, kick finishes. When it works, everything moves FORWARD. That’s the key word. The higher you come out of the water, the more energy you burn fighting drag instead of covering distance. Undulation has two jobs: getting you into a stronger catch position, and lifting your head for a breath. Nothing else. Read also: 2 different types of Undulation in Butterfly
When swimmers force the wave — bending too hard at the knees or lifting too aggressively — they don’t just risk breaking the rule. They break the stroke.
Technique Takeaway Think forward, not up.
The rule requiring both arms to move together is one of the defining characteristics of Butterfly — and it’s also where many swimmers lose efficiency.
In Freestyle, you can recover from small timing errors because the stroke is alternating. In Butterfly, you don’t have that luxury. If one arm is even slightly off, the entire stroke falls apart.
FINA Rule SW 8.2 “Both arms shall be brought forward simultaneously over the water and brought backward simultaneously under the water throughout the race.”
The simultaneous movement forces you to apply force evenly through the water. Think of the pull as an X pattern.
Your hands enter thumbs-down, a little outside your shoulders.
Sweep out to the widest point – should like a ‘Y’.
Pull down and back under your body, as the second kick fires.
Then push out narrow past your hips to finish.
Three steps, both sides, every time, together.
Instead of thinking about pulling hard, think about holding water and pressing your body past your hands. When done correctly, it doesn’t feel like you’re muscling through the stroke — it feels like you’re connected to it.
Technique Takeaway The X isn’t just a drill cue. It’s the shape that makes simultaneous power possible.
Butterfly Rules under both USA Swimming (101.3.3) and FINA (SW 8.3) require that the legs move together in a dolphin kick, with no alternating or Breaststroke movement allowed. But the rule doesn’t tell you how to time that kick — and that’s where most swimmers struggle.
FINA Rule SW 8.3 “All up and down movements of the legs must be simultaneous. The legs or the feet need not be on the same level, but they shall not alternate in relation to each other. A Breaststroke kicking movement is not permitted.”
There are two kicks per stroke cycle, and they are not equal.
The first kick happens as the arms enter. Your body is in a near-horizontal position — almost streamline — so it comes naturally. It sets up the catch. It’s a timing kick, not a power kick.
The second kick is harder. By the time it needs to fire, your body has already risen to breathe and your arms are mid-pull. You have to kick down to drive the arms through the pull and start the recovery forward. Most swimmers either forget it entirely or let it fade to save energy — which is exactly when Butterfly Starts to feel like survival.
The fix isn’t kicking harder. It’s connecting the second kick to the arm movement so both happen together, as one system. When that timing clicks, the stroke suddenly feels lighter and the arms almost lift themselves.
Technique Takeaway The first kick sets you up. The second kick saves you. Don’t drop it.
Both USA Swimming (101.3.4, 101.3.5) and FINA (SW 8.4) require a two-hand touch at every turn and at the finish. This is one of the most common areas for disqualification, especially under pressure.
USA Swimming 101.3.4 / FINA SW 8.4 — Turns “At each turn the body shall be on the breast. The touch shall be made with both hands simultaneously at, above, or below the water surface.”
USA Swimming 101.3.5 / FINA SW 8.4 — Finish “At the finish, the body shall be on the breast and the touch shall be made with both hands simultaneously at, above, or below the water surface.”
Beyond legality, these rules reinforce proper body position and timing. Approaching the wall, the swimmer must stay square and connected through the stroke. Reaching with one hand or gliding in disrupts momentum and costs time on both the touch and the push-off.
The best swimmers maintain their stroke rhythm all the way into the wall. They don’t hesitate or reach — they commit to the final stroke, make a clean two-hand touch, and transition quickly. A strong finish isn’t about stretching for the wall. It’s about carrying speed into it.
Technique Takeaway Practice your turns at race speed. If you only practice them slowly, your body won’t know what “connected” feels like when the pressure is on.
For practical purposes, the Butterfly Rules under USA Swimming and FINA are nearly identical. Both require the same body position, arm movement, kick pattern, and two-hand touches at turns and finishes. Here’s a quick side-by-side:
| Element | USA Swimming | FINA (SW 8) |
| Start | Forward start (101.3.1) | Forward start (SW 4.1) |
| Body position | Must remain on breast (101.3.2) | Must remain on breast (SW 8.1) |
| Arm movement | Simultaneous, over the water (101.3.2) | Simultaneous, over and under water (SW 8.2) |
| Kick | Simultaneous up/down, no alternating (101.3.3) | Simultaneous up/down, no alternating (SW 8.3) |
| Underwater limit | 15 meters / 16.4 yards (101.3.2) | 15 metres (SW 8.5) |
| Turns & finish | Both hands, simultaneous touch (101.3.4/.5) | Both hands, simultaneous touch (SW 8.4) |
So instead of trying to memorize two separate rulebooks, focus on understanding the movement principles behind them. If your technique aligns with those principles, you’ll be legal—and fast—no matter where you compete.
There’s always debate in swimming about how much to focus on technique versus conditioning. Some coaches prioritize yardage; others focus heavily on drills and mechanics.
Here’s the reality: in Butterfly, you can’t separate the two. The rules force a specific structure, and your technique has to work within that structure if you want to be efficient. You don’t lose Butterfly at the arms. You lose it at the timing — and timing is something you have to train deliberately, not just accumulate through yardage.
At Swim Like a Fish, this is exactly how I approach stroke development. I don’t just teach what Butterfly should look like — I teach why it works the way it does, and how to build that into your training step by step. Because once you understand the connection between rules and movement, you stop fighting the stroke and start working with it.
Butterfly doesn’t improve through effort alone. It improves through awareness.
The next time you’re in the water, don’t try to fix everything at once. Focus on one piece of the pipeline. Feel how your chest, hips, and kick link together. Pay attention to whether your arms are truly moving in sync. Notice whether you’re carrying speed into the wall or losing it.
One piece at a time. That’s how the pipeline gets built.
Butterfly isn’t supposed to feel like survival. When your technique aligns with the rules, the stroke starts to feel connected, controlled, and — believe it or not — efficient. That’s when you stop just getting through Butterfly and start swimming it well.
Structured coaching is where that shift happens. Here’s where to go next:
How to Swim a Faster Butterfly in 90 Days →
Virtual Swim Lessons — Personal Feedback & Weekly Progression →
