A man – later identified only as 'Victor', a crew member from France – had fallen from a cruise ship in the area, and Leo and his mates were the only ones to receive the call and head out in search of the missing man.
After reportedly searching for hours, one of Leo's pals spotted 24-year-old Victor, who had been treading water since his fall. They pulled him to safety.
"[Leonardo] saved the life of a man overboard who, incredibly, had survived by treading water for 11 hours. Leonardo’s boat was the only vessel looking for him,' a source told The Sun.
"The Club Med cruise worker had fallen overboard after too much alcohol and a long night... The captain put the man's chances of survival at one in a billion — like winning the lottery twice."
Not surprisingly, Victor – who had fallen from the Club Med yacht near St Martin and was picked up near to Saba Island, around 50km away – was grateful to his saviours.
"I should have died," he is said to have sobbed as he was pulled onboard and given clothes and food.
According to The Sun's source, Victor, was "minutes" from drowning when help arrived.
"The captain of his ship sent out a panicked emergency message and Leonardo and his team agreed to look for the poor guy. They were the only responders, and his only chance of survival, despite being hours away."
Leo, Camila and co. plucked him from the sea just as night was falling, and a storm was about to hit.
Leonardo, 45, and Camila were vacationing in the area ahead of the Golden Globes on January 6, where Leo was nominated for a Best Actor gong – but failed to take home the prize.
The pair have been quietly dating since December 2017, and 22-year-old model and actress Camila is currently paving her own way in Hollywood, with her film Mickey and the Bear set to be released later this year.
Opening up about what she envisions for her future, Camila told WHO: "Maybe not a long list of kids, maybe a short list of kids and a long list of movies … have a husband and have kids and be a huge actor and have a life."