Irwin, world-famous for his daring stunts with dangerous animals, died on September 4, 2006 after being stabbed in the heart by a giant stingray while filming on the Great Barrier Reef in Queensland.
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As the nation marked Father's Day on Sunday, his daughter, Bindi Irwin, who was eight years old when her father died, wrote a tribute on Instagram and Twitter alongside an image of her beaming father carrying her as a baby:
"You'll be my hero for my entire existence. I love you more than words can describe."
The 18-year-old, a media star, promotes her father's conservation causes.
Irwin's close friend and manager John Stainton, who was with Irwin when he died, said it was still "hard to talk about" what happened.
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"It was never a put on, he was larger than life in life," Stainton added, speaking to ABC radio on Friday.
"He burnt a hole in the fabric of our lives as he jumped through the television and grabbed you by the scruff of the neck. He had that magnetism and there was nothing like him before."
Irwin's son, Robert, told the Brisbane Times news website he was working towards being a wildlife photographer to "carry on in his (father's) footsteps".
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Earlier this week, Irwin's father Bob released a letter his son wrote to his parents when he was 32 to thank them for their support, but which he only found this year.
"Probably one of the most unfortunate things in a bloke's life is that it takes over 30 years to realise how essential you have been to build my character, my ethics and, most importantly, my HAPPINESS," Irwin wrote.
Other Australians took to social media websites to recall where they were when they heard the news of Irwin's sudden death, while sharing their appreciation for his conservation efforts.
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