Nixon took the lead after the first turn and never looked back on her way to winning in a time of 1 hour 55min 25sec at Clearwater Bay.

She withstood a late challenge from team-mate Michelle Burn, who came second in 1:55:41.

Defending world champion Teneale Hatton of New Zealand rounded out the podium in 1:56:16.

"World champion - I think I’m going to cry," Nixon said.

"I’ve been waiting to hear that all my life.

"It sounds amazing.

"I had to talk to myself quite a lot.

"There was never room for complacency."

The under-23 title went to Sweden’s Linnea Stensils, a 200 metres World Cup gold medallist earlier this year, in 2:00:51.

"I didn’t know when I crossed the finish line that I was first in the under-23," Stensils said.

"I need to improve my aerobic capacity so this is very good training for me.

"It’s been good for me, motivation for going out at home in the cold.

"I’ve done three ocean races and all of them have been flat.

"Hopefully next time there will be some waves."

South Africa’s Kyeta Purchase finished second in 2:04:17, while France’s Laury Marie Sainte came third in 2:09:04.

The under-18 crown was won by South Africa’s Sabina Lawrie, who triumphed in 2:05:25.

Australia’s Georgia Sinclair finished second in 2:06:13, while South Africa’s Zara Wood came third in 2:18:29.