The McKeon siblings have a famous swimming heritage with parents Ron and Susie (formerly Woodhouse) having both swam for Australia as has uncle Rob Woodhouse, all of whom were watching from the stands on Thursday. Both have come into their own during the past year, charging up the world rankings and showed that form when David won his 400 metre freestyle heat in three minutes 45.23, more than one second ahead of next fastest qualifier veteran Canadian Ryan Cochrane (3:46.62).

David McKeon, who had a relatively disappointing world championships last year, which were his first major meet, showed in not being unsettled by a reasonable fast previous heat, which included teammate Mack Horton, who made the final in 3:47.33.

"I only really saw what Mack went when because I looked at the top five times and I know that I can go faster in the mornings. I proved that at trials so I had that in the back of my mind," David McKeon said.

"I took it out and just went strong in the back end. It was a good way to blow out the cobwebs I guess.

"I'm pretty happy with that. I raced it well and I didn't take too much out of me . I slowed down a far bit in the last 50.

"I sometimes think the heats are the hardest things, just to blow the cobwebs out after not racing for a while and travelling."

Jordan Harrison, who like Horton was taken by surprise by the fast times on the first morning, qualified eighth fastest for the final.

Emma set a new Commonwealth Games record when she won her heat in 1:56.57 with England's Siobhan O'Connor second fastest in 1:56.58. Australian teammate and London Olympic bronze medallist Bronte Barratt scrapped into the final in eighth in 1:58.71.

"I was surprised by the speed of the morning but I'm happy with my swim and pretty excited for tonight," Emma McKeon said.

Christian Sprenger however was not as happy with his 200 breastroke heat. The 100 breaststroke world champion had somewhat reluctantly included the four-lap event into his schedule for the Games after impressive performances at the national titles in April and only just made the final in the final position in 2:11.96.

"I thought it would have been a bit easier but it wasn't," said a clearly frustrated Sprenger.

"At various points in the race I wanted to hold back but then it was too late and I just wasn't swimming how I should swim my own race and that's the problem," Sprenger said.

"The second I move away from what I know best, things start to occur and if you look around at people and see what they're doing you could lose the race and I think that's what I got caught up doing."

"Depending on the outcome tonight this may or may not be my last one. I'll try and come back and give it another go but I just don't think it's quite what I want to do. I think 100 metres is where I want to be, on top of the world ... but I'm going to give it everything and I want to go out swinging."

In other races, the Australian 4x100 women's freestyle relay team smashed the Commonwealth Games record in posting a time of 3:34.57, more than six seconds ahead of second fastest England, and that was without first choice swimmers Cate and Bronte Campbell.

Keryn McMaster was the fifth fastest qualifier and Jessica Pengelly, sixth, in the 400 individual medley behind local hope Hannah Miley, who was another who set a new Games record.

Josh Beaver, Mitch Larkin and Ben Treffers all qualified for the semi-finals of the 100 backstroke while Olympic and world championships silver medallist Alicia Coutts was the fastest qualifier in the 100 butterfly while Emma McKeon and Ellen Gandy, who missed a berth in the 400 individual medley final, also made it through to the final.

Leiston Pickett, Sally Hunter and Lorna Tonks qualified for the 50 breaststroke semi-finals while Jayden Hadler, Christopher Wright and Kenneth To also progressed to the 50 butterfly semi-finals.

Rowan Crothers, Matt Cowdrey and Brenden Hall qualified in the top three positions for the para-swimming 100 freestyle final (S9).