Even Mack Horton doesn't know how fast he will be in the 1500m freestyle final at the Rio Olympic trials in Adelaide after surprising himself in Wednesday's heats.
Horton had already made Rio rivals sit up and take notice with a world class 400m freestyle win on the opening night of the eight-day trials.
Now Horton plans to turn heads again with a fitting finale to the Olympic selection meet on Thursday night judging by his 1500m heat time.
The 19-year-old blew off the cobwebs by clocking 14 minutes, 48.77 seconds - the world's second fastest time of the year.
Horton hinted that the sky was the limit for the final.
"I am just going to go as hard as I can and see where I end up," he said.
His personal best (14:44.09) sits third on the Australian all-time 1500m list behind just Grant Hackett (14.34.56) and Kieren Perkins (14:41.66).
Horton has already leapfrogged Hackett on an all-time list at the trials.
He produced a 3:41.65 PB to claim 400m freestyle gold on the opening night.
He overtook Hackett to move to No.2 on the Australian all-time 400m list behind only the great Ian Thorpe.
The 400m win earned selection on his first Olympic team.
Now he has his sights set on the 1500m list after fully overcoming a gastro bug that sabotaged his 2015 world titles campaign in Russia.
"After being sick last year I had less training, so I thought the 400m would be in a better place than the 1500m but now I have no idea," Horton said.
"That (heat time) was 10 seconds faster than I expected."
Meanwhile, Cate and Bronte Campbell (25.11 seconds) could not be separated ahead of Wednesday night's 50m freestyle semi-finals.
Cate Campbell backed up from Tuesday night when she clocked her fastest time since claiming the 2013 world title and upstaged her sister Bronte to win the 100m freestyle final.
The sisters' 100m top-two finish booked not only individual but 4x100m relay Rio nods.
Cameron McEvoy (50m freestyle), world champion Emily Seebohm (200m backstroke) and Jess Ashwood (800m freestyle) highlight Wednesday night's action which features seven finals.