Tennis players typically use the off-season to rest and recover from their punishing schedules but two-time Grand Slam champion Naomi Osaka says she suffered a "near-death experience" while paddleboarding with her sister in the Caribbean.

The 22-year-old world number four, who begins the season at the Brisbane International this week, said they had been on vacation in the Turks and Caicos Islands when the incident happened.

"She made me paddleboard and then the current took us and I almost died," Osaka said in an interview with the WTA website. "I've never gone paddleboarding. I don't like the ocean like that ... So we went paddleboarding next to the house.

"Suddenly we hit a current and I'm freaking out a little bit because the house is getting further ... I'm like, 'how far out are you trying to take us?'... the water is black and the house is like a tiny dot, and I can't really swim that well."

Osaka said things took a turn for the worse when she fell into the water and panicked.

"Now I'm thinking about all the sharks in the Caribbean and I was screaming at her," she added, laughing. "'If I die, this is on you. You're going to have to tell mom how I died in the Turks and Caicos.'

"I get back on the board and then she decides that she wants to say that she sees a shark, so now I'm screaming and crying. I was fine, though, because I'm here. But in that moment I just really thought I don't want to die like that."

Osaka is the third seed at the event, a traditional warmup for the Australian Open. The draw also includes Australia's world No. 1 Ash Barty and Czech Republic's Karolina Pliskova.