Australia's open water swimming ace Chelsea Gubecka has landed another world championship silver medal, losing out on 5km gold in Doha only after a thrilling duel with double champion Sharon van Rouwendaal.

But the 25-year-old Queenslander was left far from downhearted after losing out on the big prize after a thrilling sprint finale in the Qatari capital's old port, believing she's getting better with every race and well-placed for Olympic glory in Paris's river Seine.

"It means so much and I feel like I am getting better with age," Gubecka beamed, after collecting her second world championship silver following her runner's-up spot in the 10km 'marathon' at the previous edition in Fukuoka in 2023.

She fancies an update to gold is due.

"I just fell short of the finish there but I am just so stoked that I could put in a medal performance. Today's result cements that what we are doing at home is right, so I'm really happy to walk away with a silver.

"I am learning so much about the sport even still. I just enjoy the journey. It gets hard, it is a little bit more physical - but I love this stuff, I love the wind chop and now I am just going to continue the great work ahead of the Olympic Games."

It bodes well for two classic duels in the Seine, scene of the tough open water combat, in August.

Queenslander Gubecka, the first Australian athlete selected for Paris, took the fight to the Dutch all-time great van Rouwendaal over the last of three laps on Wednesday, only to be overhauled by the former Olympic champion's electric burst through the last 150 metres which earned her the 5km/10km golden double.

Attacking from the front, 25-year-old Gubecka was still more than a body length ahead turning into the final dash for the finishing boards.

"I made sure I tried to stay in that front group knowing that my speed's pretty good, I knew I could give it a really good shake," said Gubecka.

Yet the flying Dutchwoman turned on the style to power ahead and win by just over a second, clocking 57min 33.9sec.

Even at the finish, Gubecka had the strength to battle back towards van Rouwendaal and hold off the challenge of eventual bronze medallist Ana Marcela Cunha as she finished with a flourish in 57:35.0.

Gubecka's Dolphin teammate Bianca Crisp ended 24th of the 65-strong field, in 59:06.00.

"It was harder than I thought to sit and watch the 10km earlier this week so it really great to get out there," said Gubecka, who had decided to sit out the 'marathon' race to concentrate on ocean swimming's 'sprint' with Paris in mind.

The open water program finishes with the mixed 4x1.5km mixed relay on Thursday, with Gubecka likely to swim alongside Moesha Johnson, who finished fourth in the 10km event, Kyle Lee and Nicholas Sloman in a strong quartet.

In the men's 5km, Dolphins newcomer Robert Thorpe (51:59.1) stayed in touch with the lead pack to finish 16th with Bailey Armstrong (53:23.5) ending up 23rd as Frenchman Logan Fontaine struck surprise gold.