The result qualifies the Ballarat mum for the Ironman World Championship 70.3 in Florida this November.

O'Neill felt good crossing the line at Geelong's Eastern Beach, knowing she was somewhere near the top of her field, but packed up and went home.

Only when she looked up her result did O'Neill realise she had posted a personal best time and won her first title since the birth of son Chase, six months ago.

"It was a surprise," O'Neill told The Courier yesterday.

"They let the pros start five minutes ahead but there were 1200 competitors and everyone mingled everywhere at the finish."

"I knew I had finished up near the front of the girls ... I did my best time but only found that out this morning (sic) too."

O'Neill completed the 1.9-kilometre swim, 90.1-kilometre cycle and 21.1-kilometre run in four hours, 51 minutes, 23 seconds for females aged 25-29.

Her cycle time of 2:34.29 boosted her campaign with a top-three category ranking.

Enjoyment was the key to O'Neill's race.

She had not thought she was fit enough to take the title so soon after having a baby, but knew she could be in the mix, having done it all before after the birth of her eldest son Bailey, three.

Training is "squished in" when she can, usually early in the morning, around her Mum and Bub Squad fitness business and looking after her children.

She aims to average 12 hours training a week but said she should be doing 20.

O'Neill plotted her return to racing carefully.

She contested the full Melbourne Marathon in October, for fitness training, and raced an Olympic distance triathlon in Noosa last November.

Once the Geelong race started, O'Neill knew all the hard work had been worthwhile.

"Even before the race I thought `I can't be bothered' but I'm not as unfit as I thought," O'Neill said.

"I think because I had no expectations I did better."

While qualifying for Florida was an honour for O'Neill, her focus is on the full Ironman Australia Triathlon at Port Macquarie in March.

Up for grabs is a coveted spot in the gruelling Hawaii Ironman.