It is a large creature from the Australian Aboriginal mythology where their natural habitat are the billabongs, swamps and most fresh water sources of Australia. The stories of the Bunyip came from throughout Australia but with different names from different tribes and is known to be an evil spirit.
Even the Europeans that came in the early to mid 19th century has a few written accounts of the Bunyip. Though most try do try to rationalise it, saying it could be seals that stray inland. Which might be true because as we know today, seals have been found for even as far as 100 km away from the coast.
There are no consistent description on how the Bunyip looks like in folklore other than being big, scary and dangerous . So here are some of its description: it has a dog-like face, dark fur, flippers, horns or tusks and more. They would eat anything that comes near them or near the water’s edge, they would only appear at night and of course it has a blood curdling shriek.
So was it a cryptid, a spirit of the water or a stray seal? It sounds a bit like the Dobhar Chu to me but who knows?