The "sea monster" has the body of a giant eel but a head that resembles that of a crocodile. It reportedly washed up at Swansea yesterday in New South Wales.
Images of the mysterious creature have already been shared on social media more than 1150 times.
Newcastle dad Ethan Tipper posted the photo on Facebook, asking "What the f*** is this?", yesterday morning.
Some commenters say the image may have been photoshopped, while others believe it could be a large hairtale, similar to a cutlassfish.
However, Australian Museum ichthyology manager Mark McGrouther told Australian media the creature appeared to be a nocturnal feeding pike eel, which could grow to 1.8m in length, has an elongated body, a long slender jaws and large teeth.