Pool or lake, it makes no difference to Ous Mellouli.

As long as there’s water involved.

The Tunisian won the gruelling 10-kilometre race at the London Games yesterday to become the first swimmer to win medals in both the pool and open water at the same Olympics.

Having earned bronze in the 1,500-meter freestyle last week, Mellouli pulled away from a small group of leaders in the fifth of six laps and won in 1 hour, 49 minutes, 55.1 seconds in the murky waters of the Serpentine in Hyde Park.

It was the second gold of Mellouli’s Olympic career. He won the 1,500 at the 2008 Beijing Games.

“Nothing compares to this,” Mellouli said. “There’s no way I can top this achievement.”

Mellouli overcame shoulder and elbow injuries before the games, plus a virus two days ago. Now, he’s considering retirement.

“Only those close to me know how much I struggled to get here today,” Mellouli said. “I don’t think there’s a better way to go out than this. I can just leave it all behind and have no regrets.”

After pulling himself up on to the makeshift finishing dock, Mellouli flexed his muscles, beat his chest and let out a few screams — then yelled again after getting the gold medal hung around his neck — marking Tunisia’s first victory of the games.

The country has been in a state of unrest since the fall of autocratic leader Zine El Abidine Ben Ali in January 2011 sparked the Arab Spring.

“I hope every Tunisian watching on TV today could share in my pride and joy,” Mellouli said. “We definitely needed that.”

Beijing bronze medalist Thomas Lurz of Germany took silver this time, 3.4 seconds behind, and first-time Olympian Richard Weinberger of Canada was third, 5.2 seconds back.

Alex Meyer of the United States finished tenth. Meyer was good friends with teammate Fran Crippen, who died in an open water race two years ago.

The only previous swimmer to win medals in both the pool and open water at the Olympics was David Davies of Britain. He took bronze in the 1,500 free at the 2004 Athens Games and silver in the inaugural 10K Olympic race in Beijing four years ago.