Australian naturalist and television personality Steve Irwin has been killed by a stingray during a diving expedition off the Australian coast.
Mr Irwin, 44, died after being struck in the chest by the stingray's barb while he was filming a documentary in Queensland's Great Barrier Reef.
Paramedics from Cairns rushed to the scene but were unable to save him.
Mr Irwin was known for his television show The Crocodile Hunter and his work with native Australian wildlife.
Police in Queensland confirmed the environmentalist's death and said his family had been notified. Mr Irwin was married with two young children.
Mr Irwin's manager John Stainton told the BBC the stingray's barb had pierced the personality's heart.
"He came over the top of a stingray and a barb, the stingray's barb went up and put a hole into his heart," he said.
"We got him back within a couple of minutes to Croc 1, which is Steve's research vessel, and by 12 o'clock when the emergency crew arrived they pronounced him dead."
The incident happened at Batt Reef, off Port Douglas.
Australian Prime Minister John Howard said he had known Mr Irwin well, and that the country had lost a "wonderful and colourful son".
"I am quite shocked and distressed at Steve Irwin's sudden untimely and freakish death", he said.
"It's a huge loss to Australia - he was a wonderful character, he was a passionate environmentalist, he brought entertainment and excitement to millions of people."
The stingray is a flat, triangular-shaped fish, commonly found in tropical waters.
It gets its name from the razor-sharp barb at the end of its tail, coated in toxic venom, which the animal uses to defend itself with when it feels threatened.
Attacks on humans are a rarity - only one other person is known to have died in Australia from a stingray attack, at St Kilda, Melbourne in 1945.
"Stingrays only sting in defence, they're not aggressive animals so the animal must have felt threatened. It didn't sting out of aggression, it stung out of fear," Dr Bryan Fry, Deputy Director of the Australian Venom Research Unit at the University of Melbourne said.
Experts say that while painful, stingray venom is rarely lethal and it would have been the wound caused by the barb itself, which could measure up to 20cm long, which proved fatal.
Members of the Dasyatidae family of cartilaginous fish, with about 70 species worldwide
Mostly found in tropical seas, but exist in freshwater too
Feed primarily on molluscs and crustaceans on sea floor
Swim with flying motion using large pectoral wings
Usually docile, not known to attack aggressively
Equipped with venom-coated razor-sharp barbed or serrated tail, up to 20cm long
"What happened to Steve Irwin is like being stabbed in the heart. It has little to do with the venom and all to do with the trauma caused by the barb of the stingray," Dr Geoff Isbister, a clinical toxicologist at the Mater Hospital in Newcastle, Australia, said.
Mr Irwin had built up what was a small reptile park in Queensland into what is now Australia Zoo, a major centre for Australian wildlife.
He was famous for handling dangerous creatures such as crocodiles, snakes and spiders, and his documentaries on his work with crocodiles drew a worldwide audience.
But he also courted controversy with a series of stunts.
He sparked outrage across Australia after cradling his one-month-old son a metre away from the reptile during a show at Australia Zoo.
An investigation was launched into whether Mr Irwin and his team interacted too closely with penguins and whales while filming in the Antarctic, but no action was taken.
Foreign Minister Alexander Downer praised Mr Irwin for his work to promote Australia.