Irwin developed a reputation as the "Crocodile Hunter."

SYDNEY, Australia (CNN) -- Tributes from around the world are flowing in for Steve Irwin, the enthusiastic Australian "Crocodile Hunter" who enthralled audiences around the world with his wildlife adventures.

Irwin died Monday morning after being attacked by a stingray while shooting a TV program off Australia's north coast.

Irwin's manager and friend John Stainton said Irwin died doing what he loved -- filming life in the wild.

Typical of the hundreds of tributes that have been e-mailed to CNN.com is this one from Tina Treece of Pittsburgh, Pennsylvania: "Crikey, I miss him so much already."

From Auckland, New Zealand, Ashwin Prabhu writes: "To most of us he appeared immortal, always one step ahead of every animal he encountered."

Australian Prime Minister John Howard, who knew Irwin and his family well, praised him as a "passionate environmentalist" who promoted a serious conservation message.

"He made an extraordinary contribution to creating a widespread appreciation of the value and uniqueness of Australian wildlife," Howard said.

Foreign Minister Alexander Downer said his friend Irwin was "always the showman" who was generous with his time in promoting Australia.

Actor Russell Crowe told Australian media Irwin was "the Australian we all aspire to be."

Irwin was snorkeling at Batt Reef, a part of the Great Barrier Reef offshore from the town of Port Douglas, when the incident happened.

"He came over the top of a stingray that was buried in the sand, and the barb came up and hit him in the chest," Stainton said.

U.S.-based television company Discovery Communications said it planned a marathon showing of Irwin's programs on its Animal Planet network to honor him.

Irwin was in the area to film pieces for a show called "The Ocean's Deadliest" with Philippe Cousteau, grandson of Jacques, according to Stainton.

But weather had prevented the crew from doing work for that program, Stainton said, so Irwin decided to do some softer features for a new children's TV show he was doing with his daughter, Bindi.

Wildlife documentary maker Ben Cropp, citing a colleague who saw footage of the attack, told Time.com that Irwin had accidentally boxed the stingray in. "It stopped and twisted and threw up its tail with the spike, and it caught him in the chest," said Cropp. "It's a defensive thing. It's like being stabbed with a dirty dagger." (Read the TIME.com obituary.)

Irwin was pulled from the water by a cameraman and boat crewman. He died as he was being rushed to a nearby island for emergency treatment. Attempts to resuscitate him were unsuccessful.

Queensland Police Services confirmed Irwin's death and said his family had been notified. (Gallery: The life of the "Crocodile Hunter")

Irwin was director of the Australia Zoo on Queensland's Sunshine Coast. He is survived by his American-born wife, Terri, and their two children, Bindi Sue, born in 1998, and Robert (Bob), born in December 2003.

"The world has lost a great wildlife icon, a passionate conservationist and one of the proudest dads on the planet," Stainton told reporters in Cairns, according to The Associated Press. "He died doing what he loved best and left this world in a happy and peaceful state of mind. He would have said, 'Crocs Rule!' " (Watch a remembrance of Steve Irwin -- 1:58)

"Steve was a larger-than-life force. He brought joy and learning about the natural world to millions and millions of people across the globe," said Discovery Communications founder and chairman John Hendricks in a statement. "We extend our thoughts and prayers to Terri, Bindi and Bob Irwin as well as to the incredible staff and many friends Steve leaves behind."

Cousteau's office issued a statement that he is "still in Australia with the family of his friend, Steve Irwin. It was a tragic ordeal for everyone on the boat that morning. All of our thoughts are now with Steve's family."

Discovery Communications said it will rename the garden space in front of Discovery's world headquarters in Silver Spring, Maryland, the "Steve Irwin Memorial Sensory Garden."

The company also is looking at the creation of a Steve Irwin Crocodile Hunter Fund. The fund will support wildlife protection, education and conservation, as well as aid Irwin's Australia Zoo and provide educational support for Bindi and Bob Irwin, the company said.

Irwin became a popular figure on Australian and international television through Irwin's close handling of wildlife, most notably the capture and relocation of crocodiles.

Irwin's enthusiastic approach to nature conservation and the environment won him a global following. He was known for his exuberance and use of the catch phrase "Crikey!" (E-mail us: How will you remember Steve Irwin?)

"His message is really about conservation: He really wants to leave the world a better place for everybody," Animal Planet's Maureen Smith told CNN.com in April.

"It's unbelievable, really," Jack Hanna, the host of "Jack Hanna's Animal Adventure" and director emeritus of the Columbus (Ohio) Zoo, told CNN. "You think about Steve Irwin and you think of people who are invincible."

Hanna, a friend of Irwin's, noted that Irwin's persona of the Crocodile Hunter was no act. Irwin grew up around crocodiles, snakes and other animals at his parents' Queensland Reptile and Fauna Park and had been handling such creatures since he was a child.

"Steve really knew what he was doing. He was one of the finest reptile people in the world. He knew more about reptiles than anybody did. He was raised that way," said Hanna.

Though stingrays can be threatening, their sting -- usually prompted by self-defense -- is not often fatal. The bull ray that apparently stung Irwin was "a one-in-a-million thing," Cropp told Time.com. "I have swum with many rays, and I have only had one do that to me." (Watch a marine biologist talk about the dangers of stingrays -- 3:48)

"A wild animal is like a loaded gun -- it can go off at any time," Hanna said. "You have to be careful of that." But, he added, it's not the animals who are inherently dangerous, but the way they may react around humans. "People use the word 'dangerous,' and that sometimes is a word that's not fair to that animal, because that animal is only using the defenses that God gave it," said Hanna.

Rise to popularity

Irwin became popular with his show "Crocodile Hunter," which first aired on Australian TV in 1992. Eventually, the program was picked up by Discovery in the United States, establishing Irwin worldwide.

His popularity led to a film, "The Crocodile Hunter: Collision Course" (2002).

Irwin was caught in a minor flap in January 2004 when he held his then 1-month-old son while feeding a crocodile at his Australian zoo. (Full story)

In 2003, Irwin spoke to the Australian Broadcasting Corp.'s "Australian Story" television program about how he was perceived in his home country.

"When I see what's happened all over the world, they're looking at me as this very popular, wildlife warrior Australian bloke," he told the ABC.

"And yet back here in my own country, some people find me a little bit embarrassing. You know, there's this ... they kind of cringe, you know, 'cause I'm coming out with 'Crikey' and 'Look at this beauty.' "

At Australia Zoo at Beerwah, south Queensland, floral tributes were dropped at the entrance, where a huge fake crocodile gapes, the AP reported. Drivers honked their horns as they passed.

"Steve, from all God's creatures, thank you. Rest in peace," was written on a card with a bouquet of native flowers.

"We're all very shocked. I don't know what the zoo will do without him. He's done so much for us, the environment and it's a big loss," said Paula Kelly, a local resident and volunteer at the zoo, after dropping off a wreath at the gate, according to the AP.

"He has left a legacy: That people do love some of the unloved animals like crocodiles and reptiles that people wanted to kill," Stainton told CNN.

"He's actually put a position in their hearts for them. I want that to continue. ... I want people to really go out there and remember Steve Irwin for what he really was, which was a great conservationist, saving wildlife and actually promoting wildlife that people didn't love."