Charismatic and a natural leader, the dual snowboarding world champion and Olympic flag bearer was found underwater on an artificial reef off Palm Beach on Wednesday morning.

Known more by his nickname "Chumpy" than Alex, the popular 32-year-old Pullin won world titles in 2011 and 2013 and carried Australia's flag into the opening ceremony at the 2014 Winter Olympics in Sochi, Russia.

"Chumpy was a champion bloke as well as being a champion athlete. He had great charisma that allowed him to be a natural leader," Australia's veteran Winter Olympic chef de mission Ian Chesterman said.

"His enthusiasm was infectious and his impact on Olympic sport can't be overstated."

Mr Chesterman said it was "an incredibly sad day".

Former slalom ski world champion and independent federal MP Zali Stegall tweeted it was a "very sad day for Aussie sport".

"We don't get many athletes in winter sport of his standard," Ms Stegall wrote.

Snow Australia says the community is shocked and saddened by the triple Olympian's death.

"Our deepest condolences are with Alex's family, as well as his teammates and support staff," the body said in a statement.

"Alex was a beloved member of the Snow Australia community and he will be dearly missed."

NRL great Wendell Sailor described Pullin as "one of the nicest humans I've ever met".

The Australian Institute of Sport passed on condolences to Pullin's family, friends and the whole winter sport community.

Olympic champion Steven Bradbury said Pullin will be sorely missed and was everyone's best mate.

"The world will miss such a talented human and a double world champion without ego and without selfishness who is everyone's best mate - which isn't always the case with elite athletes," Bradbury told news website InQueensland.

Police have confirmed Pullin was unconscious when he was dragged from the water at Palm Beach around 10.40am on Wednesday.

"Another diver was out there and located him on the sea floor and raised the attention of nearby surfers who sought lifeguards to bring him in," an officer told reporters.

"He didn't have an oxygen mask, we understand he was free diving and spearfishing out on the reef."

Paramedics and lifeguards performed CPR, but he was pronounced dead just before 11.15am.

Pullin was raised in the foothills of the Victorian Alps in Mansfield, the support town for the Mt Buller ski resort in Victoria.

His parents owned and ran a ski shop in Mansfield and, according to his website, he learnt to ski at the age of three.

He took up snowboarding when he was eight.

Australian Associated Press