Alex Pullin, a three-time Winter Olympian and two-time world snowboard champion, died at the age of 32 on Wednesday.
The Associated Press reported police said Pullin drowned while spearfishing in his native Australia and was found by a snorkeler.
According to police, Pullin, who was diving on an artificial reef at Palm Beach on Australia's Gold Coast, was unresponsive when taken from the water and received CPR from paramedics. Police said Pullin did not have an oxygen mask and had been freediving when he died.
"Our deepest condolences are with Alex's family, as well as his teammates and support staff," Snow Australia, the country's winter sports body, said. "Alex was a beloved member of the Snow Australia community, and he will be dearly missed."
Pullin represented Australia in the 2010, 2014 and 2018 Winter Olympics in the men's boardercross events, finishing in the top 10 in 2018.
He was also his home country's flag-bearer at the 2014 Sochi Winter Olympics and won gold medals at the 2011 La Molina and 2013 Stoneham world championships.