What kind of creature is this?

A mysterious creature that looks more like an animal out of a myth book rather than a real life creature was found washed ashore on the banks of Lake Macquarie in New South Wales in Australia.

Ethan Tipper snapped an image of the creature before posting it online to see if anyone could identify it. The creature has a long, slender body with scales and a tail like a crocodile with no legs, a head shaped like a dolphin's and a mouth full of razor sharp teeth. Can anyone identify this animal ?