Underwater Dolphin Kicks: The 15-Meter Rule Is Your Speed

Imagine This

You're on the blocks for the 100m freestyle at a big meet. The horn sounds, you dive, and for the next few seconds, you're in a silent world. You kick underwater, feeling the water rush past. You surface at exactly the 15-meter mark, and you're already ahead of the swimmer next to you. That's not luck—that's technique. The underwater phase is where races are won, and the 15-meter rule is your secret weapon.

The Rule That Defines Your Race

World Aquatics states that in all strokes, you may stay fully underwater for no more than 15 meters after the start and each turn. That's the limit, but most swimmers don't use it. They pop up early, losing the speed advantage of the underwater kick. I've seen it time and again: swimmers who surface at 10 meters, or even 5, while their competitors glide on. The rule isn't a restriction—it's a guideline for maximizing speed. If you're not using every inch of that 15 meters, you're leaving time on the table.

The Physics of Speed

Why is underwater kicking so fast? Because you're avoiding the drag created by breaking the surface. In a 50m pool, you have a start and one turn in a 100m race. That's two chances to go underwater for 15 meters each—that's 30 meters, or 30% of the race, spent in a streamlined position. The front crawl is the fastest stroke on the surface, but a well-executed dolphin kick underwater is even faster. It's no wonder that elite swimmers like Pan Zhanle, who set the 100m freestyle world record of 46.40 seconds at the 2024 Paris Olympics, have exceptional underwater kicks (Reuters).

Training the Underwater Phase

So how do you train to maximize your 15 meters? It's not about endless yardage; it's about specific, purposeful work. Start with your streamline. Your body should be a straight line, arms extended, head between your biceps. Then, work on your dolphin kick. The kick originates from your chest, not your knees. Practice kicking on your side and on your back to build core strength. Do sets of 25m underwater kicks, counting your strokes. Aim to reach the 15-meter mark consistently. In practice, use a measured rope or markings on the pool deck to check your distance. Your goal is to surface just at the 15-meter mark, not a meter short.

The Turn: Your Second Chance

The turn is where you can gain even more. In backstroke, you must break the surface at or before the 15-meter mark after the turn (World Aquatics). In freestyle, you can do a flip turn and then kick underwater. But here's a tip: don't rush your turn. Many swimmers sacrifice their underwater phase to get into the turn quickly. That's a mistake. A smooth, fast turn that sets you up for a powerful underwater kick is worth more than a frantic, sloppy turn. Practice your turns so that you leave the wall in a tight streamline, with a strong push, and then immediately start your dolphin kick. Count your kicks—elite swimmers often take 10-15 kicks to cover 15 meters.

The 15-Meter Rule in Open Water

The 15-meter rule doesn't apply to open water, but the principle does. In open water, you don't have walls to push off, so you have to generate speed from a standing start. But you can still use underwater kicks after a dive or a turn around a buoy. The key is to stay streamlined and efficient. Open water races are freestyle events, so you can use any stroke, but the underwater dolphin kick can give you a burst of speed to break away from the pack (World Aquatics Open Water Swimming Rules).

What I'd Actually Do

Here's my recommendation: make the underwater phase a priority in every practice. Dedicate at least 10% of your training to underwater kicking, both on your front and your back. Use fins to build leg strength, but also do some without fins to feel the water. Measure your distance and time your kicks. Aim to be consistent at 15 meters, not just occasionally. And when you race, commit to that underwater phase. Don't surface early because you're tired—push through. The 15-meter rule is your speed, so use it.

Sources

• World Aquatics - https://www.worldaquatics.com
• Olympic swimming pool specifications (Wikipedia) - https://en.wikipedia.org/wiki/Olympic-size_swimming_pool
• World Aquatics Swimming Rules Reference Card (2023-2025) - https://eastswimming.org/wp-content/uploads/2024/04/WA-Swimming-Reference-Card_13072023-Large-Print-Bold.pdf
• Reuters - https://www.reuters.com/sports/olympics/swimming-chinas-pan-obliterates-100m-freestyle-world-record-gold-2024-07-31/
• World Aquatics Open Water Swimming Rules - https://www.aquaticapaulista.org.br/arquivos/2025/2025082012255.pdf