Lee and Rio Olympic champion Sharon van Rouwendaal sprinted to the timing wall together, with the Dutch defending champion just pipping the Australian for the silver medal by 0.8 seconds in the 10-kilometre open water race at Tokyo’s Odaiba Marine Park.

It’s Australia’s first-ever medal in marathon swimming.

“I don’t really think I’ve processed how it feels – it’s just incredible,” 27-year-old Lee said.

“It was the goal going in to come out with a medal and doing it at my first Olympics is incredible.”

With swimmers starting early Wednesday in water temperatures already at 29 degrees – just under the allowable limit of 31 degrees – Lee was in touch with the leaders throughout.

The Queensland school teacher made her move on the final lap, breaking away with Cunha and van Rouwendaal.

Cunha’s winning time was one hour 59 minutes 30.8 seconds.

Lee was immediately on the phone after the race to her coach John “JR” Rodgers, with the 82-year-old legendary swim coach unable to travel to Tokyo due to poor health.

Cunha won her first medal in her third Olympics. She was 10th five years ago in Rio de Janeiro and fifth in the 2008 Beijing Games.

Lee said she had prepared for the conditions by training in a heated pool, while she also spent time in Darwin before travelling to Tokyo.

“We were expecting the water temperature to be about 31 degrees because that’s what it was at the test event,” she said.

“So I’ve been training in a pool that was 31 degrees and the last couple of weeks leading in I went to Darwin which is similar air temperature to here.”

But she did get one surprise – hit by a large fish, with a number spotted jumping out of the water along the course.

“It jumped up and hit me (on the chest) – I didn’t know what it was at first and I was like ‘Woah’.

“I was watching them jump out before but I didn’t think one would actually hit me.”