Slovenian Martin Strel completed his swim of the entire 5,265km Amazon River, his son said, a 65-day odyssey in which he battled exhaustion and delirium while trying to avoid piranhas and the bloodsucking toothpick fish.
Averaging about 80km a day since he started stroking in the Amazon's Peruvian headwaters on Feb. 1, Strel fulfilled his goal near the city of Belem, 2,440km north of Rio de Janeiro. If confirmed by Guinness World Records, it will be the fourth time the 52-year-old has broken a world swimming distance record.
"He's hit point zero," Martin's son and project coordinator, Borut Strel, said by telephone from the Amazon on Saturday, the world's second-longest river after the Nile. "There will be a ceremony Sunday in Belem, but he finished today."
In 2000, Strel swam the length of Europe's 3,004km Danube River and then broke that record two years later when he swam 3,797km down the Mississippi. And in 2004, he set a new world record after swimming 4,003km along China's Yangtze.
Strel's health worsened on Thursday evening, as he struggled with dizziness, vertigo, high blood pressure, diarrhea, nausea and delirium, his Web site said.
But despite having difficulty standing and being ordered not to swim by his doctor, Strel insisted on night swimming to finish the course.
Guinness spokeswoman Kate White said the organization would analyze data expected from Strel and his support team to determine whether he had established a new record. She said it usually takes six to eight weeks to review such applications.
Strel's staff plans to send Guinness the required documents by the first week in August.
Speaking by satellite phone during a break aboard his support vessel on Thursday, Strel said the journey became tougher as he approached Belem.
"The finish has been the toughest moment so far," he said, when he was still about 100km from the finish line. "I've been swimming fewer kilometers as I get closer to the end. The ocean tides have a lot of influence on the river's currents and sometimes they are so strong that I am pushed backward."
He said he was lucky to have escaped encounters with piranhas, the dreaded bloodsucking fish that swims into body orifices, and bull sharks that swim in shallow waters and can live for a while in fresh water.
"I think the animals have just accepted me," he said. "I've been swimming with them for such a long time that they must think I'm one of them now."
Strel, who lost about 12kg, said there were times in which he was in so much pain "I could not get out of the water on my own ... Once, they had to take me to the hospital to check my heart. But everything turned out okay."
He was also tormented by cramps, high blood pressure, diarrhea, chronic insomnia, larvae infections, dehydration and abrasions caused by the constant rubbing of his wet suit against his skin, his Web site said.
To cope with delirium, Strel said he turned to his doctor and therapist for help.
"My doctor, who is a psychotherapist, talks to me, asks about my pains and redirects my thinking to other things," Strel said.
"It definitely helps to have someone to talk to when I'm not in the water," he said.
Just days after he began swimming, Strel also developed second-degree burns on his face and forehead, and his team feared the burns would develop into third-degree burns and become infected.