Backstroker Corey Main has qualified for his second semi-final at the Rio Olympics and Bradlee Ashby will also get a night swim after making the cut for the 200m individual medley.

The 21-year-old Main clocked another personal best to post the 15th-fastest time in the heats of the 200m.

While Ashby, 20, came within a whisker of his national record to book the last spot in the 16-man semi-final on Wednesday night.

Main's time of 1 minute 57.51 seconds in his favoured event allowed him to finish sixth in his heat and book another visit to the night finals in the Olympic Aquatics Stadium.


"I came home strong and felt good. I did a PB so I'm happy. I need to do big PB tonight but I am up for it," he said.

Russian Evgeny Rylov was quickest in the heats with a time of 1:53.02. Florida-based Main took 0.28sec off his previous best and is now just 0.36sec shy of Gareth Kean's national record.

Main also made the semi-finals of the 100m and ended 15th overall. Ashby was seventh in his heat won by US legend Michael Phelps with a time of 1:59.77 and was just 0.01sec outside his NZ mark.

He snuck into the last 16 by just 0.03sec.

American great Ryan Lochte was fastest qualifier with 1:57.38.