The fish kick may be the fastest subsurface swim stroke yet (2015)
71 comments
·July 12, 2025cjcenizal
bravesoul2
Does that give advantage to those in the middle lanes?
foobarbecue
Middle lanes are faster, and for some reason swimmer with the fastest record gets the middle in most events, which always seemed weird to me -- it's a positive feedback system. Seems like you should give the advantage to the people who are behind, not ahead... but that's common in sports and in modern society for some reason.
GolfPopper
It seems like the objectively fair solution is that everyone swims the exact same lane in a still pool and is timed.
Scarblac
It's strange to reward slower contestants in sports.
dsamarin
I want to see world records get broken
messer979
“To him who has much, even more will be given. To him who has little, even what he has will be taken away”
vikingerik
If slower qualifiers got better position, then what you'd get would be qualifiers deliberately trying to sandbag themselves for that. Such an incentive is never a good look for sports.
jstanley
> Seems like you should give the advantage to the people who are behind, not ahead...
Lol? How did you work that one out?
By extension, should the olympics be comprised entirely of each country's worst athletes?
onlypassingthru
Any turbulence created by waves and vortices smashing into hard surfaces is going to slow the swimmer down. To paraphrase an old adage, smooth is fast.
mojomark
I'm inclined to concur with onlypassingthrough. If the resulting wake is similar to fish locomotion (e.g. thunniform or similar) vortices will shed off in a Karmen Vortex Street that spreads laterally with distance behind the swimmer (potentially into other lanes, and propulsive efficiency of propulsors are generally less efficient in turbulant vice laminar open-water flow... but not always, it can depend on the 'structure' [how chaotic] the flow is).
The magnitude of the energy in that turbulent wake will depend on how efficiently the oscillating fin interacts with water over time to produce forward thrust. The cool thing about oscillating foils as opposed to rotating thrusters, is that when the fin 'swoops' once it creates Vortex 'A' spinning clockwise, and when it 'swoops' back the result would be a Vortex 'B' spinning counterclockwise, and the two vortices will partially cancel out. That cancellation serves to recover energy from Vortex 'A' and the energy is transferred back into forward thrust.
In other words, fish tails create trails of contrarotating vortices and continually push off of them. It's like walking up a springy staircase, where each step you make, a little energy is recovered to bounce you up to the next step.
In theory, if you had a swimmer in front of you, generating a Karmen Vortex Street and not effectively canceling out those vortices, but instead just shedding vortices, you can use the energy from the swimmer in front of you to 'spring' yourself forward - barely using any energy yourself. Those complex hyrdodynamic relationships could be why some swimmers/flyers tend to fly in specific formations with other animals in their school/flock.
Bottom line, I would bet that any residual vortices that spread into adjacent swimming lanes will tend to interact chaotically and result in unstructured turbulance, which should yield less optimal swimming conditions for swimmers in those lanes.
analog31
Indeed, and as a consequence there are rules for who gets which lane.
nkrisc
I thought the comparison to running was interesting. As an almost exclusively terrestrial mammal, there is a very natural way for us to run. No one is going to discover than running on our arms and legs is faster, or something other than ”unnatural” way of running is faster.
But that’s not really the case with swimming. We didn’t evolve a natural swimming instinct or form for speed.
When I learned that (nearly?) all terrestrial mammals can swim to some degree (even ones that look like they shouldn’t be able to - like ungulates), I was a bit surprised, but it’s not too surprising upon reflection. But that got me thinking then: what is the best terrestrial mammalian body plan that also happens to be good for swimming? What terrestrial mammal would also be fast swimmers if they could learn and train for it as humans do? Maybe my thinking is clouded by anthrocentrism, but the human body plan which is good for bipedal running also seems to work out pretty well for swimming.
Of course, top human swimming speeds are pretty terrible compared to human running speeds and the swimming speed of basically any other aquatic animal, but we’re not made for it!
CorrectHorseBat
>No one is going to discover than running on our arms and legs is faster, or something other than ”unnatural” way of running is faster.
Surprisingly not everyone seems to be convinced of that
Rendello
A few years ago I tried out TikTok and quickly came to see that there are huge niches inside the platform that are barely even searchable or existent outside the app. One of which was these videos of people sprinting or galloping on all fours. It's fascinating and terrifying seeing people who've practiced do the movements, it's uncanny in both how natural and unnatural it can look. It seems to be an intersection of unconventional exercise enthusiasts and furry-types.
Sprinting: https://www.youtube.com/shorts/6S0ctkOixj8
Galloping / jumping: https://old.reddit.com/r/toptalent/comments/ldxsoz/these_peo...
quuxplusone
Very cool! Reminds me of Tim Burton's "Planet of the Apes" (2001), which did quadrupedal running with practical effects — harnesses, towed treadmills, all sorts of tricks — i.e., cheating, from the POV of this thread. :)
"Behind the Scenes of Tim Burton's Planet of the Apes": https://www.youtube.com/watch?v=KighzjHkZtY&t=803s "Ape School" starts at 9m35s. Quadrupedal running starts at 13m23s.
codingdave
I just went down a small rabbit hole, watching some videos of quadrupedal running, and what struck me was how un-balanced the motion looked. Even the guy who is (one of) the world's fastest has this weird twist in his back while he is doing it, to make sure his knees and elbows don't smack together. That may be sustainable when you are young and strong, but I worry this guy, or anyone else who gets into this, is going to be wracked with long-term damage and in a lot of pain when older.
bmacho
It's okay if the best motion is not symmetric. The swimming in TFA isn't symmetric either.
quuxplusone
Ryuta Kinugasa, Yoshiyuki Usami. "How Fast Can a Human Run? Bipedal vs. Quadrupedal Running." Frontiers of Bioengineering and Biotechnology 4:56 (June 2016).
That looks remarkably like an April Fool's article released at the wrong time of year. The second-to-last paragraph is where they reveal the joke to anyone who wasn't already in on it:
> This study has limitations. Although statistical models are significantly related to mathematical formula [sic], the use of a statistical model to accurately predict future athletic performance is challenging (Hilbe, 2008). Fitted linear models should be treated with some caution. The use of linear regression for world record modeling would yield a continued decline that would eventually become negative, thus suggesting that update of world records can be continued until 0 s. It must also be noted that quadrupedal world records did not exist before 2008. This relatively recent involvement [sic] of quadrupedal running results in a somewhat tenuous comparison of world record times. Therefore, despite a high coefficient of determination, a large diverging confidence interval was found.—
—and then right back into it—
> —The 95% confidence intervals [sic] indicates that projected intersects could occur as early as in 2032 (9.238 s) or as late as 2076 (9.341 s).
A "rebuttal paper" might accept their major premise (i.e. feasibility of "a statistical model to accurately predict future athletic performance") but argue that rather than fitting a straight line (linear regression), we should fit an exponential decay curve (exponential regression). In an appendix, we'd try fitting a hyperbola (y = K1/(x-X0) + K2), taking X0 for quadrupedal running at 2008 and X0 for bipedal running anywhere from 2 million to 10 million years ago.
In an alternative "experimentalist approach," the rebuttal paper's author would actually run 100m himself, first on two legs and then on four; plot these as an additional data point (with x=2025) in each set; and fit a polynomial to that data. This would likely change the conclusion quite drastically. ;)
ethan_smith
Bears, particularly polar bears, are terrestrial mammals with impressive swimming capabilities - they can swim up to 60 miles without rest and use a modified dog paddle that's remarkably efficient.
Etheryte
This is a stretch for what you might consider terrestrial, but polar bears swim faster than olympic athletes. Moose also swim hella fast, so funnily enough it's the same guys in water as on land that you have to look out for.
navbaker
I had no idea how enormous moose were until I had to go to Fairbanks a few years ago for a work thing. It was unreal sitting in line waiting to move through the gate at the air base and seeing a moose casually running down along the 8 foot fence along the perimeter and realizing it was taller than the fence!
chrisco255
Beavers, with their wide flat tails, are very good swimmers. Looking it up though it seems black bears are the fastest overall although I believe beavers are the fastest relative to their body size.
chrisco255
The human body plan is also pretty good for climbing. The dynamism of the human body is why we thrive in so many environments.
bmacho
> The dynamism of the human body is why we thrive in so many environments.
I'd say it's our hand to make tools, our brain to plan, and out throat/mouth to communicate
cratermoon
> When I learned that (nearly?) all terrestrial mammals can swim to some degree (even ones that look like they shouldn’t be able to - like ungulates)
Even elephants can swim. https://www.youtube.com/watch?v=HpD40ewOyC4
comrade1234
> I reach out to Misty Hyman, who won gold in the 2000 Olympics...
Her name always makes me laugh because I then think about her brother's name: Buster.
GLdRH
Have you ever heard of Fanny Chmelar?
maxden
In what sport does she compete for Germany? https://www.youtube.com/watch?v=U_Klz5qncZQ
bravesoul2
Misty could mean smoky too!
fouronnes3
Really would love to see a true freestyle category — with the 15m rule removed. I'm curious why it's not a thing.
onlypassingthru
I think the rule was created because underwater racing is not that interesting to watch for spectators and more difficult to officiate from the surface. Maybe all we need is a bunch of GoPros stuck around the pool and we can see a new race category?
aleph_minus_one
> I'm curious why it's not a thing.
According to onlypassingthru in https://news.ycombinator.com/item?id=44542370 "The optics of an underwater race were not good".
Additionally consider (as was pointed by swarnie in https://news.ycombinator.com/item?id=44542285 ) that there exist clothing restrictions in Olympic swimming - in my opinion this is also a contradiction to the spirit of "freestyle".
noahjk
> there exist clothing restrictions in Olympic swimming
My argument against this is that there are already so many activities where less wealthy are priced out. Most prospective athletes (or families) don't have a bunch of money to shell out for stuff like hydrophobic full-body suits, or hockey gear, or whatever.
fainpul
Reminds me of the fascinating efficiency of fish, where even a dead fish can swim upstream, given the right kind of vortices.
I wonder how much potential for improvement there still is for the human body.
https://fyfluiddynamics.com/2018/07/when-i-was-a-child-my-fa...
onlypassingthru
IIRC, the backstroke races at the 1996 Olympics were pushing the boundaries of human potential as competitors swam some or all of the races underwater. The optics of an underwater race were not good (ha!). As a result, FINA made it mandatory to surface and compete in actual backstroke instead of underwater dolphin kick.
swarnie
What improvements are you thinking?
I see three avenues:
1) Clothing - Already banned in the Olympics
2) Medication - Also officially banned in the Olympics but the Enhanced Games look like a promising test bed.
3) Go full Cult Mechanicum?
refulgentis
Dumb q, never learned to swim and don't understand the sport contextually.
Given:
"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."
This is used to explain a conclusion used throughout the rest of the article, namely, the dolphin/fish strokes aren't useful in competitive swimming because people using them have to surface.
But I don't understand: the rule says swimmers performing the backstroke have to surface, and when I look up backstroke, it is someone laying on their back? Which doesn't sound like either of these
senkora
These short videos should clear it up:
Backstroke start technique: https://www.youtube.com/watch?v=xwq-IsGNa28
Backstroke flipturn technique: https://www.youtube.com/watch?v=B-WNtRGwSjQ
Underwater dolphin kicks can be done on your front, back, or (I guess) side, so it also works for backstroke. And the way that starts and turns work in backstroke still puts you underwater at the start of each lap.
bryancoxwell
Very cool. Should probably have a (2015) though.
null
yawpitch
Hmm, divers have known the dolphin kick for years (decades?) as a way to move underwater at speed, but you’re rarely near the surface or the bottom to have effects from the surface interfaces. Interesting.
MengerSponge
(2015 article)
I get that it's a quirk of the sport's history, but it's funny and dumb that swimming awards medals and records for being the fastest at a slower stroke. It's like if track meets would have a 100m sprint, a 100m skip, and a 100m run-backwards.
If I could change things in the world, I wouldn't eliminate the extraneous strokes in swimming, but I would include additional competitions in all the track distances: backwards running, handstand walk, and one-legged hopping.
djmips
Olympics have different 'strokes' used between sprint, middle distance, long distance, hurdles, steeplechase and walking races - so there is some variety in the locomotion forms unlike your strawman.
nasmorn
The walking race is the only one where there are specific rules. The other races just happen to mostly favor a style. Sprint finishes in long distance races are common and legal
bee_rider
It is annoying that rules were added to the “freestyle” race, to preclude these new better underwater forms of swimming. Freestyle ought to mean you are free to pick any style.
mikeytown2
The rule is only on the IM; freestyle can't be butterfly, backstroke, or breaststroke.
bee_rider
They added a rule in 1998, you can only go 15 meters underwater after the flip. Although I guess there are safety concerns, which seems reasonable…
aleph_minus_one
But why do we need this rule if front crawl is faster anyway?
jccalhoun
I think there are too many swimming events in the Olympics. If the same few people win most of the medals then maybe the events are too similar.
Please eliminate two. PS I am NOT a crackpot
wrboyce
I couldn’t agree more!
nkrisc
Seeing backwards running races would be impressive. Seeing the fastest human runners is also very impressive, but it’s also less interesting in a sense because they’re doing exactly what our bodies evolved to be able to do. It is interesting to see that ability pushed to its natural limits, but I think it’s a bit more interesting to see people excel in things we didn’t evolve to do: like swimming or running backwards.
aleph_minus_one
> Seeing backwards running races would be impressive.
For cars, such races seem to exist (have existed?) in the Netherlands:
> Dutch Reverse Racing
> https://www.youtube.com/watch?v=lLgPTJWAysY
These kinds of races seemed to be popular in the Netherlands because DAF (a Dutch manufacturer) produces the Variomatic transmission system
> https://en.wikipedia.org/wiki/Variomatic
"Because the system does not have separate gears, but one (continuously shifting) gear and a separate 'reverse mode' (as opposed to reverse gear), the transmission works in reverse as well, giving it the side effect that one can drive backwards as fast as forwards. As a result, in the former Dutch annual backward driving world championship, the DAFs had to be put in a separate competition because no other car could keep up."
bravesoul2
Diagonal running!
airstrike
I can't wait for you to find out there are different kinds of track competitions.
bix6
Swimming needs a corkscrew race!
Butterfly is my favorite. It’s so fun to fly through the water like that.
joelwilliamson
My daughter’s school had a race day to wrap up their swimming lessons, and one of the events involved rolling from front to back every second stroke. It was funny to watch but not very practical.
adelmotsjr
It is also my favorite, despite being the hardest due to the high skill required to do the proper technique. It is so awesome to feel so powerful.
Sharlin
Well, race walking is also a thing. And, although not fully analogous, track and field has hurdles.
eesmith
1500 meter running and 1500 meter race walking are two track events with different ambulatory styles.
Amazing! This is about the dolphin kick performed on its side, rechristened “the fish kick.” I couldn’t fathom (ha) why the same kick rotated 90 degrees could be faster but it turns out that the kicking motion is constrained by the motion of the water around it. In the dolphin kick, the water moves up and down and is limited by the water’s surface and pool’s bottom. The swimmer frees themself of these constraints by turning on their side.