The grace and power of a powerful underwater dolphin kick is a sight to see. It’s smooth, powerful, and extremely fast in the right hands (and feet).
But how far should you really kick underwater off each start and wall? At what point does it actually end up slowing you down?
Swimmers can dolphin kick underwater up to 15m, but how many kicks they take comes down to kick velocity, event distance, surface swim speeds, and stage of the race.
Here’s what swimmers should know about figuring out how long they should dolphin kick under the surface.
For more guidance on faster underwaters, check out our detailed guide on improving the underwater dolphin kick.
The Dolphin Kick is a Weapon (Until It Isn’t)
At the Rio Olympics in 2016, Michael Phelps showed yet another reason for why he is the greatest swimmer of all time.
In the final of the 4x100m freestyle relay, Phelps went into the turn almost neck and neck with France’s Fabien Gilot, the Frenchman 0.13 seconds ahead.
Both swimmers pushed off, and instead of surfacing like most of the other sprint freestylers in the field, Phelps stayed submerged, unleashing 9 vicious dolphin kicks that sent him hurtling into the lead. When Phelps exploded to the surface, the United States suddenly had a sizable lead that they would not relinquish on their way to the gold medal.
It was a feat made all the more extraordinary considering the competition Phelps was against—Gilot is absolutely no slouch in the sprint freestyle.
And while we might have gotten used to seeing Phelps demoralize and thrash the competition off the walls, that doesn’t mean that we should be trying to completely emulate his way of doing things.
In fact, extending our dolphin kicks means that we slowing down below surface swimming speeds, accumulating more CO2 for no tangible benefit, and leading to slower overall performances.
Why Longer Underwaters Aren’t Always Faster
We know that underwater dolphin kicking is generally faster than on-the-surface swimming.
But only if:
- You actually kick faster underwater than you swim.
- You surface before decelerating below swim speeds
- You’re conditioned for it.
A study (Veiga et al., 2016) published in the European Journal of Sport Science analyzed the underwaters and results of the 100m and 200m events at the 2013 FINA World Championships in Barcelona.
In the 100 events, faster swimmers were not kicking out further and longer—at this level, a lot of swimmers are pushing the 15m limit on starts and turns.
But what separated faster swimmers from slower ones was that they were kicking faster under the surface. Kick out distance wasn’t the difference-maker—kick out speed was.
This is an important distinction. Grinding out a couple of extra kicks per wall to kick out further—but with reduced velocity—is obviously not the same as covering that same distance with explosive, efficient kicks.
When it comes to dolphin kick distance: Quality > quantity every time.
For the 200m events, things changed a little bit. In the butterfly and backstroke events, faster swimmers did travel longer distances underwater.
In the 200m freestyle events, the fastest female swimmers actually used shorter turn distances with faster velocities, suggesting an alternate strategy for full-race success.
The key insights is that long swimmers dolphin kick under the surface is highly event specific. The goal is fast performances, and not just hitting an arbitrary target distance.
The Metabolic Cost of Longer Underwaters
Kick velocity and deceleration are the big reason to keep your underwaters honest–but what is the metabolic cost of staying underwater longer?
A study (Venckunas & Achramavicius, 2024) had competitive swimmers do a fast 200m freestyle twice–once with 5m underwaters off every wall, and again with 12.5m underwaters.
Speed, pace, and time was held constant. Blood lactate more than doubled with the longer underwaters (7.9mmol/L versus 3.3mmol/L).
Those longer underwaters cut off gas exchange, meaning that while the muscles are working, oxygen is being consumed, and CO2 keeps accumulating, the ventilation needed to clear that debt is temporarily off-line.
This is why distance swimmers rarely go beyond 5m after turns, even though they could go up to 15m and that dolphin kicking is generally faster than surface swimming. The metabolic cost isn’t worth it–much better to protect the aerobic engine for the laps to follow.
The Final Turn is Where the Chlorinated Toast is Buttered
The final turn in the 200m races was where elite kickers really separated themselves from the field. Backstrokers in particular saw longer underwaters on the final turn associated with a 2.3% improvement in overall race time.
Why the last turn? Your muscles are aching, your legs are turning to cement, and hitting that final turn for one last breath-hold is brutal. Being able to win this turn and underwater is a pretty strong sign that you’ve properly trained for the specific demands of this race.
Training specifically for that turn—doing long, fast underwaters while fatigued and not just when you are fresh—is something you should prioritize to be race-ready.
Surface Before You Slow Down, Not After
Distance is one thing—but knowing when to surface based on velocity is another. The standard advice of when to surface is when your underwater speed slows to match your surface swimming speed.
Makes intuitive sense, but that’s not what elite swimmers do. And it’s not what you should do either.
Race data from the men’s 200m freestyle final at the Paris Olympics showed that all eight finalists consistently surfaced before their underwater velocity dropped to match their surface swimming speed.
When swimmers surfaced, they were consistently moving faster than surface swimming speed.
| Start | First Turn | Second Turn | Third Turn | |
| David Popovici | 3.29m/s | 2.36m/s | 2.39m/s | 2.44m/s |
| Matthew Richards | 3.29m/s | 2.29m/s | 2.43m/s | 2.33m/s |
| Luke Hobson | 3.33m/s | 2.43m/s | 2.48m/s | 2.46m/s |
Clean swimming speed was around 1.8m/s.
These athletes weren’t squeezing every last drop of distance from their underwaters, but were using them strategically, surfacing while still moving fast to carry momentum into their first strokes.
And that’s why surface timing matters–because those first couple of strokes are the fastest strokes you will take all lap.
Another study that looked at performances 2013 World Championships analyzed 112 races across all the 100m events.
Breakout stroke speeds—those first 1-2 strokes after surfacing, were faster than mid-pool speeds:
- Male freestylers — 2.17 m/s at breakout vs. 2.04 m/s mid-pool
- Female freestylers — 1.90 m/s vs. 1.79 m/s
- Male butterfly — 2.13 m/s vs. 1.86 m/s
- Female backstroke — 1.79 m/s vs. 1.60 m/s
That’s a free 5-10% speed boost at the surface, but swimmers can only cash it in if they don’t wait too long to surface and are forced to re-accelerate up to speed.
Surface at the right moment, and you plant your first stroke while you’re still flying.
Train for Underwater Distance the Smart Way
Instead of just kicking out to a specific distance on each lap, bring a performance-focused mindset to your underwater dolphin kick.
This means:
- Know your numbers. Have your coach time you kicking as fast as possible to 7.5m, 10m, 12m, and 15m. Compare those times to your surface swimming velocity. That data tells you where your underwaters stop paying off.
- Surface just before you decelerate. The goal is to break out faster than surface swimming speed—not equal (or worse, slower) to it. Become aware of when your kick starts slowing down, and aim to surface just before that happens.
- Your underwaters should align with the constraints of the event. 50 freestylers for example, tend to benefit from shorter underwaters, unless of course you are a first-ballot Hall of Fame underwater specialist like Gretchen Walsh, whose underwaters are the best in the world, or Caeleb Dressel, who pairs an explosive start with thunderous dolphin kicks for superior underwaters.
- How long you stay underwater should also be based on oxygen demands. Consider the oxygen demands of the race and the trade-offs that come with extended underwaters. For example, distance swimmers will go into oxygen debt very fast if they do long, extended underwaters every turn, starving their aerobic engine.
- Using a kick count in practice — Kick counts are essential for faster dolphin kicking. Elite swimmers from Ryan Murphy to Gretchen Walsh to Maggie Mac Neill used them in practice to boost kick repetitions and also get comfortable kicking fast and long under all types of situations in training.
- Developing a more powerful kick — Resisted dolphin kicking sets (with DragSox, resistance tubing, drag chutes, etc) build more power in your kick. Pair with targeted strength training in the gym to increase force from the muscles that work during the dolphin kick.
Dolphin Kick with Purpose
Don’t feel like you have to do a ton of underwater dolphin kicks just because the greatest swimmer in the history of the sport has mastered it.
See Also: 10 Minutes a Day to a Faster Underwater Dolphin Kick
George Bovell, a 5-time Olympian from Trinidad and Tobago was aware enough to know that during his 50m freestyle races he was faster at the surface. Bovell, who swam a 21.00 short course 50 free, would explode to the surface almost immediately off the start, foregoing the dolphin kicks altogether.
Gilot, when paired up against Phelps, surely knew that trying to get head to head underwater with a lifelong dolphin kicker like Phelps was pointless, and that he was better off getting to the surface quickly.
The underwater dolphin kick will continue to be a critical part of swimming (and when comparing race data from the Paris 2024 Olympics vs 2013 Worlds, swimmers are relying on the dolphin kick more than ever).
The goal isn’t to kick as far as you can. It’s to kick as fast as you can for as long as it’s actually helping you.
Know your speeds, train your underwaters under fatigue, surface at the right moment, and let your breakout strokes do their job.
THE DOLPHIN KICK MANUAL
The Ultimate Guide to an Explosive Underwater Dolphin Kick
Fast underwaters are crucial for success on race day. But most swimmers don’t know where to start.
The Dolphin Kick Manual is your express ticket to gold-medal underwaters. Technique, sets, dryland–you’ll learn exactly what it takes to build an elite underwater dolphin kick.
WHAT’S INSIDE
- Learn elite dolphin kick technique
- How to train tempo, undulation, and more
- Dryland specific for UDK
- 20 proven sets to get you started
- Breath control, resisted kicking, and more
- 6-week action plan to get you started
AS SEEN IN
220+ pages. Evidence based. Pure thunder kicks. Instant access.
