Bindi Irwin Marks 18th Birthday With Tribute to Late Father Steve Irwin

— -- Happy 18th birthday, Bindi Irwin!

The daughter of the late Crocodile Hunter Steve Irwin shared an adorable baby photo on Instagram on Sunday and paired it with a touching caption paying tribute to her father, Steve Irwin.

"Our Dad, Mum's soulmate and a superhero for us all, passed away," she wrote. "However, since this photo was taken, 18 years ago, one life ingredient has remained, unchanged, unbreakable. That is the unconditional love that is shared between my beautiful little family and the loyalty we have to each other and everyone else who has taken this journey with us."

Irwin added that she is "endlessly grateful" for her parents and the love that surrounds her.

Irwin was 8 when 10 years ago her father was killed by a stingray.

She followed up with a second post of a more recent picture and a note about her future as an adult.

"Being 18 and embarking upon my adult years, I can't predict what life will have in store for me. All I know is that I will try my very best to make a difference in this world with each moment that I'm given," she wrote.

Just a few days earlier, Irwin posted a similar throwback photo in honor of her mother's birthday.