The 15-meter rule is a part of most swimming events, including backstroke, butterfly, and freestyle races. (Breaststroke swimmers have more strict rules that apply to their underwater strokes.) But where does this 15-meter rule come from and why is it applicable?  How can you take advantage of it in your own swimming?

Here’s everything you need to know about the 15-meter rule.

Dolphin Kick

Introducing the dolphin kick.

20 years ago, an American swimmer named David Berkoff made an observation about swimming and decided to put it into practice. "It seemed pretty obvious to me that kicking underwater seemed to be a lot faster than swimming on the surface," he said in an interview with NPR. He began to experiment with spending more and more of his race underwater, and the powerful edge it gave him paid off.

In 1988 he broke the 100-meter backstroke world record at the Olympics … by spending most of the race underwater. Soon after, the 15-meter rule was applied to backstroke events, in order to allow swimmers to take advantage of the powerful start it offers, while still making sure that the race is primarily about backstroke skill, instead of turning into a submerged dolphin kick race with a bit of backstroke tacked onto the end.

Submerged swimming today.

These days, the benefits of the dolphin kick are widely recognized and used across all strokes that allow for it. The 15-meter rule has similarly expanded to include butterfly and freestyle races. American swimmer Michael Phelps made waves at the 2016 Olympics not only for his numerous medals but for spending more time underwater than any other competitors in the 4x100 meter freestyle relay.

Due to his build and comfort with underwater swimming, Phelps’ dolphin kick is more powerful and efficient than many other people’s, making it an effective strategy for him even in shorter freestyle races, in which most swimmers surface more quickly.

kicking underwater

What’s the science behind the dolphin kick?

So why is underwater kicking faster than swimming on the surface? When you break the surface of the water, you create waves, which in turn create more drag, slowing you down a bit. Add up all that drag over many strokes, and it can add up to a significant amount of time lost, especially at elite levels where success is often measured in hundredths of a second. On the other hand, swimming below the surface also means that the swimmer isn’t breathing during that time. The ideal balance between efficient movement and cardiovascular efficiency will be different for each swimmer.

Getting used to the 15-meter rule.

While the use of the dolphin kick is now limited to 15 meters, that’s not a reason to avoid using it. It’s a powerful tool for getting a strong start after diving or turning. Still, nobody wants to be disqualified for using it just a hair too much. Competition pools have clear marks at the 15-meter point, and it makes sense to practice as you plan to compete, being sure to surface before that marker.

If you practice in a pool that doesn’t have permanent markings at 15 meters, ask if they’d consider adding them (or if you can get permission to add a temporary marker, such as duct tape. Of course, markers aren’t helpful if you can’t see them. A good pair of non-fogging goggles is critical if you want to avoid that disqualifying line.

The rules and science of swimming are always changing.

In such a dynamic sport, we expect new breakthroughs regularly. Who knows? Maybe you’ll be the one to discover the next one. Of course, there’s only one way to find out: gear up and jump in.