The man who witnessed the last moments of Steve Irwin's life has described how a massive stingray wildly stabbed the conservationist "hundreds of times".

He also recounted the crocodile hunter's calm final words: "I'm dying."

Justin Lyons has spoken for the first time since he filmed the stingray strike out at Irwin in shallow water in far north Queensland eight years ago.

Lyons said he and Irwin had headed out from the main boat in an inflatable to find something to film when they came across a "massive" stingray in chest-high water.