There are few places where nerves are more palpable than at an Olympic trials.

The hot, chlorine-scented air inside the Brisbane Aquatic Centre is heavy with them.

The anxiety of athletes and their loved ones, milling around amongst the eucalyptus trees outside the venue, permeates in through the gates, down the grandstands' multicoloured seats and onto the pool deck, where swimmers seek final reassurance from their coaches during warm-ups in crowded competition lanes.

Inside the aging, 1982-built venue, the dreams of hundreds of Australia's most talented swimmers could be realised.

Or, more likely, dashed.

Amongst Australia's deepest-ever pool of talent, just two swimmers in each event will book their spot on the plane to Paris.

For a maximum 52 swimmers, the chance for a shot at sporting immortality awaits.

For the rest: Disappointment. Heartbreak. Empty platitudes of "maybe next time".

Of course, not everyone's chances are on quite such a knife edge.

The stars on night one were expected to shine: Ariarie Titmus, Kayley McKeown and Emma McKeon — Olympic champions all — were in action and, as expected, booked their spots in Paris at the first time of asking.

That's not to say the same nerves don't linger — Olympic champions are just as susceptible to the creeping fear that a 14-year-old making their debut at a meet of this calibre is.

Even the greatest feel the familiar butterflies dancing in their stomachs.

Even Titmus — two-time 400m world champion, defending Olympic gold medallist and reigning queen of the eight-length discipline.

But after her heat, in which she admitted that she switched off after three laps, Titmus admitted to feeling some nerves.

"It's so crazy. If I just know what I know how to do, it's just another heat swim," Titmus said.

That was despite recording a 4:01.57 — comfortably under the qualifying time and over five seconds faster than the next-quickest qualifier, Lani Pallister.

In truth, you sense it would have taken something quite remarkable — a disaster of Ian Thorpe falling off the blocks in 2004 proportions — to knock Titmus off her perch, so dominant is she in her pet event.

"It's just swimming," Titmus added.