Twenty years ago today, about 11am on September 4, 2006, Steve Irwin was fatally stabbed by a stingray while snorkelling in shallow water at Batt Reef, off Port Douglas — the barb piercing his heart as a film crew tried frantically to save him. Bindi was eight; Robert was two. On the anniversary, both have shared tributes to their father, the ABC reports, with Bindi describing him as the family's "guardian angel".

"Our family lost our superhero," Bindi wrote. "My mum lost the love of her life; my brother and I lost the greatest dad. Grief never truly leaves us; we walk alongside it every day. Where there is enormous grief, there is even greater love." Robert posted a photo of himself as a khaki-clad baby looking up at his mud-covered dad, with five words: "Your legacy is forever."

'Grandpa crocodile'

Bindi also shared a video of her father talking about the day she was born — "the most incredible wildlife experience of my life," he called it. "I swear she just fit right in here in the palms of my hands." Two decades on, she says his legacy has settled into something simpler than conservation: love. "I have a five-year-old daughter who watches his documentaries every morning," she wrote of Grace, her daughter with husband Chandler Powell. "She feels utterly loved by the 'grandpa crocodile' without having met him. Dad, I love you with my whole heart."

The men who kept up with him

For those who worked beside him, the memories run wilder. The ABC's anniversary feature finds his best mate Wes Mannion — who met a young Irwin at the then-named Queensland Reptile and Fauna Park in the mid-1980s, as a captivated 14-year-old — still carrying the physical souvenirs: scars from Graham the crocodile, who tore chunks from his leg during a flood at Australia Zoo in an incident where Irwin saved his life, and a busted rib from sparring with a boss who built a Brazilian jiujitsu cage at the zoo. "He was like my brother, my best friend, my mentor and my boss all rolled into one," Mannion said. "Most people couldn't keep up with him, but if you could do it, it was the ride of your life."

Producer and director John Stainton, who discovered Irwin on a beer-commercial shoot and turned his home videos into The Crocodile Hunter, watched those first tapes from midnight until 3am. "He mesmerised me," he said. "It was the most amazing television I'd ever seen in my life." Bob Blasdall, who edited all five seasons and the documentaries including the final film Ocean's Deadliest, put the appeal simply: "Here is this character who sucked you through the lens and plonked you in his lap and, like a Barbie doll, took you on the journey with him."

Stainton was on the boat at Batt Reef that day, and it fell to him to deliver the news to Terri Irwin. "It's a day that you can't ever think about without crying … the saddest time of my life," he said. Investigators believe the stingray may have mistaken Irwin's shadow for a shark and lashed out to protect itself.

Twenty years on, the khaki has passed to a second and now a third generation — Bindi and Robert carrying the conservation work to audiences in Australia and the United States, and a five-year-old in front of the television every morning, learning the family trade from her grandpa crocodile. "God bless you, Steve," Blasdall said. "It really was the highlight of my life."