Chloe Esposito claims Australia's first modern pentathlon medal

It was a gut feeling eight weeks out from the Olympics but Chloe Esposito knew she would win gold.

The 24-year-old became Australia's first ever modern pentathlon medallist on Friday, storming home to claim gold with a grin on her face.

It was a first place at the Hungarian championships in June that sparked the thought in Esposito's mind.

"After I crossed the line (in Hungary), I just had this gut feeling and I thought 'I think it's going to happen'," Esposito told reporters.

"This morning and yesterday before the fence I was thinking `stop thinking about this, you might jinx yourself or something'."

It had come after a rough year, with Esposito missing competitions and training with an Achilles injury.

Her sacrifices included moving to Budapest two years ago to work on her fencing and enjoy better competition, leaving her fiance and her mum back home.

Esposito's fencing improved dramatically on her London result, where she finished seventh overall.

"I was over the moon with my fencing," she said.

"I said to myself even if today doesn't go the way I want it to, I'm just happy my fencing has improved."

Esposito's golden run started with a 13th in the fencing on Thursday, before she started Friday with a powerful 200-metre swim to win her heat.

She picked up an extra point in the fencing bonus round and completed a solid equestrian lap when many other contenders bombed out.

Esposito started the combined running and shooting round in seventh place, with a 45-second handicap behind Polish leader Oktawia Nowacka.

She immediately moved into sixth and started picking off runners one-by-one before overtaking Nowacka on the final shooting leg.

"Finally I heard that they had left the shooting range and I looked back and I saw that it was quite a big distance," Esposito said.

"And I know I can run and I knew they wouldn't catch me in the last lap."

Her father Daniel Esposito represented Australia in the pentathlon in 1984 and Chloe said she could not have done it without his coaching, which he admitted was quite tough.

"That's how we train in Australia. The other (athletes) when they see it, they think it's a bit over the top, but really it's not," Daniel Esposito said.

The proud dad said it was a juggling act as a coach and a parent but the pay off had been worth it.

It's not the end for the Espositos in Rio either - little brother Max competes in the men's event on Saturday.

"He's just really cool, calm and colleted and always happy," Chloe said.

"He knows what to do, he's done it all in training before."

Fellow Australian Jarred Tallent also came close to clinching a gold of his own in the 50km walk, but was pipped just before the finish line to claim silver.

But it all went down hill for Australia's BMX riders.

BMX cyclists Sam Willoughby and Anthony Dean entered the men's final having won all three of their semi-finals.

But in the medal race, Willoughby finished sixth and Dean didn't finish.

BMX compatriots Caroline Buchanan and Lauren Reynolds didn't even reach the women's final.

And equestrian hope Edwina Tops-Alexander came ninth in the showjumping final to leave Australia 10th on the medal table midway through Friday's competition with seven gold, 11 silver and 10 bronze.

Of other Australians in action on Friday, the women's synchronised swimming team finished last in the eight-nation final.

Australian taekwondo duo Carmen Marton and Hayder Shkara suffered painful first-round defeats.

But women's golfers fared better - Su Oh shot a five-under 66 in the third round to move to four-under, five shots off clubhouse leader and world No.1 Lydia Ko.

Fellow Australian Minjee Lee was also at four-under nearing the completion of her third round.

And Australian sprint kayaker Ken Wallace and his K4 men's crew won their semi-final to advance to Saturday's final, while Stephen Bird booked a place in the men's K1 200m final, also on Saturday.