The 22-year-old handily outpaced his challengers at Yeosu EXPO Ocean Park, clocking a time of 53min 22.1sec.

Nearest challenger Logan Fontaine of France was 10.10 seconds behind, while Canada’s Eric Hedlin, the 2013 world silver medallist in the event, was just a further 0.2 seconds back in third.

Last year, Rasovszky won the 5km and the 25km open water events at the 2018 European Aquatics Championships in Scottish city Glasgow, finishing ahead of Frenchmen Axel Reymond and Fontaine in the former.

He is the only one of today's medallists who will be competing in the men's 10km event on Tuesday (July 16).

"It was a huge race - great speed, no tactical swims, just go," Rasovsky said.

"I toyed with the idea to stay a bit behind before I geared up, but there was a tremendous fight at the turns so I saw it was better to stay in front and not be part of that tussle. 

"I launched my finish a bit earlier than expected but it all worked well. 

"Now, this is a great feeling.

"This gold eases the pressure before the 10km so I think I can show my real potential there."

The first day of diving finals were dominated by China with all three gold medals going the country's way.

In the mixed 10 metre synchronised event, Lian Junjie helped retain the title he won with Ren Qian at the 2017 World Aquatics Championships in Budapest by partnering Si Yajie to a comfortable victory.

They managed a total of 346.14 points with Russia's Ekaterina Beliaeva and Viktor Minibaev distant runners-up on 311.28 points.

Mexico's María José Sánchez Moreno and José Balleza Isaias took the bronze medal with 287.64 points.

The women's 1m springboard final saw Chen Yiwen come out on top with 285.45 points.

The United States' Sarah Bacon was the silver medallist with 262 points, while Kim Suji celebrated a bronze for hosts South Korea with 257.20.

There was also success for China in the men's 3m synchronised event, through Xie Siyi and Cao Yuan.

The pair managed a total of 439.74 points to win by a margin of 24.72 over Great Britain's Jack Laugher and Daniel Goodfellow.

Rounding off the podium were Mexico's Juan Manuel Celaya Hernández and Yahel Castillo Huerta with 413.94 points.

Medals were also awarded today in artistic swimming as Russia's Svetlana Kolesnichenko successfully defended her solo technical routine world title with 95.0023 points.

Spain's Ona Carbonell finished second with 92.5002 points, while Japan's Yukiko Inui came third with 92.3084.

Competition in Gwangju is due to continue tomorrow.