I tug my black swim cap over my hair, strap on my pink goggles, and keep a focused calm, like Michael Phelps before a race. It’s lap swim on a Monday afternoon at my local YMCA, and I’m going to attempt the fish kick. Most fish move through the water with a horizontal wiggle. The fish kick challenges you to copy this movement: You completely submerge yourself underwater, position yourself on your side, keep your arms tight above your head in a streamline, and propel yourself forward with symmetrical undulations. After decades of swimming, some of it at the competitive level, I think I might have a shot. Pushing off the wall, and after what I can only describe as a struggle, the water resists my forward motion and I float to the surface, not unlike a dead fish.
Humans are land animals, and not natural swimmers. We have to learn how to swim, and it is up to us to find the fastest way to do so. The search may finally be coming to an end. In the last few decades, stroke mechanic experts have discovered that swimming under the surface is faster than swimming on the surface. “It’s hard to fathom that this could happen in track and field,” says Rick Madge, a swim coach and blogger. “Nobody is going to come up with a new way of running that is going to be faster than anything else. Yet we just did that in swimming.” And the fish kick may be the fastest subsurface form yet.
But it’s also difficult. After my failed attempt at the YMCA, I reach out to Misty Hyman, who won gold in the 2000 Olympics using the fish kick in the underwater portion of her race, and is now an assistant coach at Arizona State University. She agrees to give me a lesson at an indoor pool in New Jersey, where she is leading a swim clinic. I find her there wearing her gold medal, surrounded by young swimmers asking for her autograph. She waves me over with a smile, which puts me at ease. I almost forget that my mediocre skills are about to be scrutinized by a world-class swimmer.
It is both natural and disconcerting to see a human form move this way.
We head over to a swim lane, but before we jump in, she offers some tips. To do the fish kick, she says, I need to hinge at four places: shoulders, ribs, hips, and knees. I pull my arms together over my head to make a streamline, and tilt my head and arms back and forth in a single motion. She tells me to tighten my shoulders. I do. “Tighter still,” she says. I pull them in so hard it almost hurts. “That’s right,” she says. She tells me I’m good at the rib hinge, but it still requires my full concentration, and it feels like I’m collapsing my organs with each bend. I try the hip and knee hinges, which come more naturally.
We hop into the lane and do a couple warm-up laps. Then she shows me her fish kick. She pushes off the wall and glides away into the blue like a minnow. It is both natural and disconcerting to see a human form move this way.
Until recently, competitive swimming has focused almost entirely on what happens at the surface of the water. In early 19th-century England—which many consider to be the birthplace of the modern sport—swimmers raced using the breaststroke. A few decades later, Europeans learned a faster stroke when two Native Americans visiting London demonstrated a way of swimming they had learned growing up: the front crawl. One observer wrote, “they lash the water violently with their arms, like the sails of a windmill, and beat downwards with their feet, blowing with force, and forming grotesque antics.” The Brits eventually got over their shock. The backstroke came next, followed in the early 20th century by the butterfly stroke, which overcame the drag of the underwater recovery required by the breaststroke. The butterfly became the second fastest stroke after the front crawl.
All swimming at the surface shares the same speed restriction. “You’re always limited by your hull speed,” says Ryan Atkison, a sport biomechanist at the Canadian Sport Institute Ontario. It’s a nautical principle that also applies to swimmers. The theory goes that a swimmer on the surface cannot go faster than the bow wave that he or she creates. The bow wave increases with swim speed until, in theory, it stretches along the whole length of the swimmer’s body. Atkison says that the maximum speed is one body-length per second, which is about 1.9 to 2.6 meters per second for a swimmer about 2 meters (6 feet, 5 inches) tall.
“You can’t go any faster than that unless you climb up over top of that wave,” says Atkison. “Some animals can, like dolphins can porpoise and jump over top of that bow wave, but humans can’t physically climb out of that trough,” he says. “The only real way to get faster is to be better under water, where we don’t really have those upper limits on speed.”
Coaches began to take advantage of this fact in the 1980s, when Harvard University coach Joe Bernal realized that some of his swimmers were faster if they stayed underwater and dolphin kicked. This is essentially identical to the fish kick, except that the swimmer is flat on his stomach, rather than turned on his side. Some especially strong underwater swimmers stayed submerged almost the entire length of the pool, since there was no rule against it. That all changed in 1998, when FINA, the world governing body of competitive swimming, ruled that swimmers performing the backstroke had to surface after 15 meters.
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