Olympic champion Oussama Mellouli of Tunisia got stuck trading elbows and kicks with a French challenger.
Five-time world champion Thomas Lurz of Germany had to waste precious energy fighting off herds of competitors just to get around the buoys lining the course.
Valerio Cleri of Italy liked the event to "wrestling," and had to deal with a jellyfish sting, too.
For Spyridon Gianniotis of Greece, however, the combative nature of the grueling 10-kilometer open water marathon at the swimming world championships Monday was just the way he liked it.
So it was no wonder when Gianniotis retained his title in the discipline’s signature event, surging ahead on the final lap to avoid a sprint with Mellouli.
"You’re going to get hit, you’re going to get pushed. It’s rough," Gianniotis said. "It’s really hard, and hard is what I like."
Gianniotis clocked 1 hour, 49 minutes, 11.8 seconds in the waters of Barcelona’s harbor. Lurz finished second, 2.7 seconds behind. Mellouli was third, 7.4 back.
Meanwhile, at the splendid diving venue overlooking the city’s skyline, China captured both golds of the day, with Chen Ruolin and Liu Huixia winning the women’s 10-meter synchronized platform after Li Shixin retained his men’s 1-meter springboard title.
Chen and Liu built an unassailable points total of 356.38 by executing five nearly flawless dives to give China its seventh consecutive world title in the event.
Individually, it was Chen’s fourth straight world title in the event, adding to her four Olympic golds.
Olympic bronze medalists Meaghan Benfeito and Roseline Filion took silver with 331.41 points, and Malaysia’s Pandelela Rinong and Mun Yee Leong finished just 0.27 points behind the Canadians to claim bronze.
Earlier, Li defended his title with 460.95 points. Four-time European champion Illya Kvasha of Ukraine took silver with 434.30, and Alejandro Chavez of Mexico earned bronze with 431.55.
Later, inside the Palau Sant Jordi arena, Russia was aiming for its third consecutive gold in the team tech event of synchronized swimming.
Back down by the seaside, it was a far different open water competition from the more placid conditions of last year’s race at the London Olympics, which was held in the Serpentine in Hyde Park.
Gianniotis finished fourth in London.
"The Olympics were a spectacular event, but it was in a lake and it didn’t feel like real open water," he said.
While the race began at noon under a searing sun with an air temperature of 86 degrees, water conditions were ideal at 77.
The problems were created by the large field of 65 swimmers.
Lurz was the first to struggle, losing time early on due to the physical jockeying.
"It was very bad. And it’s always the guys not finishing in the first positions," he said. "I want to swim and not fight. It just costs power. But that’s open water."
In the final kilometer, Mellouli had to fend off some underwater kicks and jabs from Damien Cattin-Vidal of France, who finished fourth.
"Every time I tried to move he got super physical, so I couldn’t move," Mellouli said.
Cleri, who won the 25K at the 2009 worlds in Rome, also complained.
"It was almost like wrestling at the buoys," he said. "And I got stung by a jellyfish. The harbor is tight and there’s not much room to swim. When we’re that close to each other technical superiority gives way to fighting."
Mellouli won Saturday’s 5K race with an impressive sprint finish, and he was at or near the lead for much of this race. But Gianniotis took the initiative on the final lap to gain a clear lead of two body-lengths ahead of his chasers.
"I’m quite good on sprinting but not like Oussama. I knew that if it goes to the end, even if he’s more tired than me he’s got more speed than me, so I tried to stay in front," Gianniotis said.
Having skipped the 5K, Gianniotis appeared fresher than his rivals. Still, there was pain.
"I pushed a bit in the last 300 meters to make a bit of a (gap) in case (Mellouli) came really hard," Gianniotis said. "The last 50 meters I’ve never felt so bad in my life. I was nearly fainting. … My hands were (shaking).
"My heart was pumping so hard I couldn’t keep up with my blood," Gianniotis added. "I just put my head down and swam hard."
In the end, though, it was a measure of redemption after missing the podium so narrowly in London.
"It’s not the same," he said. "But I came here with only 3 1/2 months training and I won. After the Olympics I was feeling very bad psychologically, but this is sport and I said to myself I wanted to come back."