Oh, Ian Thorpe. First let’s cast our minds back (*time-travel finger-wiggle*) twelve years to the Sydney Olympics.
Thorpe was the youngest in the field at 17 but had the biggest feet out of the lot of them . You can see that outboard motor start up on his very first length, 6-beat leg kick all the way. That was just part of his normal stroke! And then on the last length it somehow still goes up a notch. No wonder no-one else came close to 3.40 for over a decade (shiny suits aside).
But… look at his turns! Thorpe barely streamlines off the wall, and although he breaks into his stroke relatively late compared to the rest of the field, he doesn’t DO anything much while he’s under the water! Only backstrokers and sprinters were really bothering with underwater fly kicks back then so it didn’t really matter in the 400m final above.
However it was noticeable when the 200m freestyler dudes were lining up at Aussie trials last week, they had super-defined six packs - except Thorpe. You can see why Touretski was trying to get him to swim butterfly in training, but I guess it was too little too late. Just look how much ground the rest of the field made up on Thorpe on his last turn (around 3.20 in) - he obviously lacked the fitness, and fell back to his old habits when exhausted (fair enough!).
I dunno. It’s fair enough to save your energy/breath if you know you’ll be swimming faster on top of the water than underneath it, but if you can do BOTH then that’s at least 0.2 of a second per turn faster than Thorpe’s world record times right there. And Sun Yang is going to do that this summer, I can guarantee it - 3.39 low at least.