Bindi and Robert Irwin honor Steve Irwin on 20th anniversary of his death

Bindi and Robert Irwin have marked 20 years since their "superhero" father, Steve Irwin, died.

The 28-year-old conservationist and TV personality commemorated the milestone anniversary on Friday by sharing a video clip of The Crocodile Hunter host describing Bindi's birth as "the most incredible wildlife encounter" of his life.

She wrote in the Instagram caption, "20 years ago, today, the world lost the most passionate and dedicated wildlife conservationist. Our family lost our superhero. My mum lost the love of her life; my brother and I lost the greatest dad."

She continued, "Grief never truly leaves us; we walk alongside it every day. Where there is enormous grief, there is even greater love. In the last 20 years, I have watched the world mourn my dad with our family. I always thought that my dad's legacy is wildlife conservation; it turns out, his legacy is love. For our planet and for each other."

Bindi noted that her five-year-old daughter Grace watches Steve's documentaries every morning and loves her "grandpa crocodile", and thanked her late father for watching over Grace.

"My dad left a lasting impact so poignant that it will ripple out for generations to come. I believe with my whole heart that his love will live on forever. In all of us. In every kindness we show to the Earth. And that is a life and legacy worth celebrating," she concluded the poignant post. "Dad, I love you with my whole heart. Thank you for being our guardian angel."

The Australian TV star died on 4 September 2006, at the age of 44, after a stingray fatally pierced his chest while he was shooting a documentary underwater. Bindi was eight at the time, and her younger brother Robert was two.

Robert posted a photo of himself as a toddler sitting on Steve's knee in a muddy woodland and simply wrote, "Your legacy is forever."

Meanwhile, Steve's widow Terri shared a snap of the famous zookeeper and told her followers that "grief still walks with me like my shadow". She concluded her caption by addressing Steve: "Until we meet again (heart emoji)."