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Steve Irwin, the Australian television star known as the "Crocodile Hunter," tangled with snakes, swam with the sharks and wrestled with crocs. The Aussie's wild adventures and his catchphrase "Crikey!" was loved by 500 million viewers in more than 100 countries.

Then, in 2006, tragedy struck the wildlife warrior. While filming a documentary on the Great Barrier Reef, Steve was struck and killed by a stingray. This 44-year-old conservationist left behind his wife, Terri, two young children, Bindi and Robert, and a lasting legacy at the Australia Zoo.

At his memorial, Steve's daughter Bindi made a promise. "I had the best daddy in the whole world, and I will miss him every day," she said. "When I see a crocodile, I will always think of him and I know that daddy made this zoo so everyone could come and learn to love all the animals. Daddy made this place his whole life. Now it's our turn to help daddy."