Amazing footage has emerged of a freediver's close call with a whopping 150 kilogram stingray that "gently nibbled" at his head near Rottnest Island.

West Australian commercial divers producing a documentary on sharks, shipwrecks and marine life were filming off Rottnest when crew member Johnny Debnam had the gigantic stingray skim over his head.

Despite feeling "a bit of a nibble" after the ray repeated the movement three times, Mr Debnam was unharmed and described the sensation as a "rush".