The Brazilian, a five-time world champion, was in a showdown with Oceane Cassignol and marginally completely the 10-kilmoetre course before the French swimmer.

Cunha touched the finishing pad with 2 hours 1min 30.30sec on the clock.

Cassignol's time was 2:1:30.80.

Germany's Lea Boy - 20 years old like Cassignol - came third, in 2:01:31.90, and the top 14 finishers were separated by fewer than 10 seconds in the open water off Katara Beach.

Boy's compatriot Leonie Beck, who won this race last year when it was the only one to go ahead before the coronavirus crisis forced the cancellation of the season, came fourth.

In the men's race there was a French victor as Olympic bronze medalist Marc-Antoine Olivier came out on top.

Olivier, who won this race in 2020, repeated the trick with a strong finish to win in 1:52:02.40.

Hungary's Kristóf Rasovszky, the world champion over 5km and series winner in 2018, led for much of the contest but had to settle for silver, 3.10sec back.

Italy's Gregorio Paltrinieri - an Olympic champion in the pool five years ago - came third.