Katie Ledecky cut an imposing figure on pool deck ahead of the Pan Pacs starting in Tokyo on Thursday. On a USA swimming squad without the retired Michael Phelps, it is Ledecky that that turns the most heads.
At just 21, the freestyle specialist already owns five Olympic golds and a swag of world records. She's virtually invincible in anything upwards of 400m and has had few worthy challengers since burst onto the scene with a surprise gold over 800m at the London Games, where she was just 15.
But two years out from the Tokyo Games, a worthy challenger may have finally emerged. Ariarne Titmus, just 17 herself, wants to bridge the gap against the American champion and will use this week's key meet to take another step on her journey.
Ledecky is mortal in the 200m, although it is there too where she owns Olympic gold. But she was beaten in the race at last year's world titles and Titmus won't race her here in Japan, with both the 200m and 800m on Thursday's opening day presenting a scheduling clash.
Titmus has already emerged as a world-class 200m swimmer and it will remain on her Olympic schedule in 2020, although she has made no secret of her desire to focus on the longer distances.
The 800m, where Ledecky is ultra-dominant, presents the most-difficult challenge. Ledecky won the race at the US trials in 8:11.5s, sluggish by her standards but still more than eight seconds clear of the best Titmus has produced.
It's a race where Titmus believes she can shed significant time and wants to at least put herself on Ledecky's radar with a big performance at Pan Pacs.
"I wasn’t quite happy with it (800m) at Comm Games, so we said we should drop the 200m, focus on the 800m and swim a better time. I haven’t quite done what I want to do in the 800 so that’s the reason why I’m targeting it more here," Titmus said.
"8.20s is my pb. The Australian record is 8.18s, which would be lovely to get that. I don’t think too much about time. I think about the process of the race and that’s something I really have to get better in the 800m so here will be another opportunity to be able to do that."
But it's the 400m where Titmus could land a significant blow. She almost broke the four minute barrier in a brilliant Commonwealth Games swim, while Ledecky has the world's best time in 2018 with a 3:57.94s.
Should Titmus continue to drop her PB and Ledecky be even slightly off her game, it may be a closer race than she's had in the event since she burst onto the scene in such emphatic style.
Titmus was fourth in at worlds last year as a 16-year-old and has endless respect for Ledecky. But she won't be intimidated once she gets onto the blocks and into her rhythm.
"Everyone is another swimmer but she is kind of special a little bit, she is very fast. And when she arrived I saw what she looked like but I don’t pay too much attention to it.
"I can only control what I can do and if she swim very fast, then good on her. If she’s not, then it gives me a great chance to try and get closer to her. I’m just going to do the best I can and see how I go."
A sub-four minute swim would certainly get the swimming world's attention. Given the tendency for young swimmers to shed time in a hurry, it's a distinct possibility, although Titmus won't be putting any pressure on herself to crack the barrier.
"It’s always on my mind but I never really say to myself 'I’m going to do it here, I’m going to do it here'. It will happen when it happens and I’ve been training really well. It’s not something I put pressure on myself to do.
"I obviously want to have it done before the Olympics but I’m not too fussed about it. I know where I’m sitting at training at the moment and I’m swimming pretty fast but you can never tell if it’s going to happen or not."