Tokyo Olympics: Second gold medal for Ariarne Titmus

The 20-year-old made Tasmanian history as part of Australia's best ever day at an Olympic Games.

Titmus became Tasmania's first multiple Olympic champion and also equalled Shane Gould and Ian Thorpe as the only Australians to claim the 200-400m double.

Having won her heat and final in the 400m, the 2019 Tasmanian Athlete of the Year made it five from five with wins in her 200m heat, semi and final.

Seventh after the first 50m, fourth at the halfway point and third at 150m, the former Riverside and Launceston Aquatic member, whose family moved to Brisbane in 2015, produced her trademark storming finish to mow down pacesetter Siobhan Haughey and claim the win in an Olympic record of 1:53.50.

Haughey (1:53.92) took Hong Kong's first swimming medal with silver and third-placed Penny Oleksiak (1:54.70) became the most successful Canadian Olympian in history with her sixth medal while five-time Olympic champion Katie Ledecky finished fifth.

An emotional Titmus hugged coach Dean Boxall and admitted it was a tight finish.

"I had Katie covered but Siobhan was the person that was there and at the end my legs started to go, but I'm happy to get it done," said the Launceston-born former St Patrick's College student.

"I'm just from a small town in Tassie and this goes to show that if you believe you can do something you can 100 per cent do it if you work for it," she said.

"I don't think it will settle in until I get home and have a rest. When you're in this situation you have to compartmentalise everything and once I stop racing I'll release everything, but for now it's onto the relay and 800 and I don't want to ruin the rest of my meeting by celebrating too hard, but I'm very proud of what I've achieved.

"Back home right before we left Sydney went into lockdown and a lot of other places are as well. It's really sad so I'm happy that the Olympics are here and we can hopefully bring some excitement to loungerooms. I'm so fortunate to be here and able to do what I love."

On the commentary team for the event, Thorpe was impressed by Titmus' ability to back up.

"To be so composed and be thinking of what the next swim is, is a talent you have and it's a very mature athlete's mindset that does that and thinks about what they can get out of the whole competition, not just that one race," he said.

Titmus became the first Tasmanian to win multiple medals at one Games. Hockey players Matthew Wells (gold in 2004, bronzes in 2000 and '08), Daniel Sproule (bronzes in 1996 and 2000) and Eddie Ockenden (bronzes in 2008 and '12) and rower Simon Burgess (silvers in 2000 and '04) won at consecutive Games.

Titmus should be in action on Thursday with the 4x200m freestyle relay final at 1.31pm before beginning her fourth event, the 800m, later that evening.

Richie Porte found solace in Ariarne Titmus' performances after what he called "the worst ride I've had in a long time" in the men's time trial.

Four days after finishing 48th in a brutal 244-kilometre road race, Launceston's 36-year-old father-of-two clocked 1.00:53 after two laps of a 22.1km course featuring 846m elevation.

It was enough for 27th overall, 5:49.48 behind Slovenian winner Primoz Roglic, who shared last year's Tour de France podium with Porte, while fellow Australian and INEOS Grenadiers teammate Rohan Dennis won the bronze medal.

"Such a hard course and been a hard last week really, but it is what it is. No excuses. This one's on me, I just wasn't up to it," said Porte, who finished his 11th Tour de France just six days before the Olympics.

"It's been a really strange Games. Bit of a shame it's during this epidemic but it's been a great experience. The Japanese have been fantastic. For me it hasn't been a great Games but still better than being in hospital like I was after the road race (on his Olympic debut in Rio)."

After 12 seasons in the elite WorldTour, Porte has a year left on his INEOS contract.

"Next year's it for me. Thirty-six, I'm not getting any younger. It's been a great career but it's definitely twilight for me."

Asked about Titmus' gold-medal showings, Porte added: "That was absolutely brilliant. We swam at the same club (although) obviously I'm a fair bit older. She's been brilliant. It's great for Launceston, you've got Ricky Ponting and Ariane Titmus, it's great to be from a great sporting city like Launnie."

Huon rower Sarah Hawe and her crewmates in the women's eights have qualified for the final in Tokyo.

Needing to finish in the top four of five crews in the repechage, the Aussies came fourth in 5:57.15, 4.16 seconds behind the winning Romanian crew with Canada and China also progressing to join reigning world champs New Zealand and Olympic champs USA, in the final. Australia will be in lane 1 at 11.05am on Friday.

Hawe, who celebrated her 34th birthday on the day of the Opening Ceremony, and her crew are hoping to build on a silver medal at the 2019 world championships.