The Hawkesbury River monster, often shortened to HRM is a long-necked river monster reported in the Hawkesbury River, a 122 kilometre long, 120 foot deep river in New South Wales, Australia. It is described as having a seal-like head with a flexible, swan-like neck, large body with patchy black and gray skin, two sets of flippers with an eel-like tail. The animal was first heard of by settlers in the 1800s, although there is Aboriginal rock art over 3-4,000 years old in the area that describes the creature. The settlers were told stories by the Aboriginals of women and children being attacked by the moolyewonk or mirreeular, both of them Aboriginal names for the animal.
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In 1912, the Sydney based newspaper, The Evening News, featured an article of a four-foot long animal described as resembling an alligator that was seen by a boating party. In 1924, a man known as W.J. Riley claimed to have seen a five to six-foot long serpentine animal swimming in the Hawkesbury River near Windsor. It was described as being “unpleasant-looking,” with sandy-coloured skin and a square-shaped, fish-like tail.

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Sightings of the Hawkesbury River monsters started to increase in the 1980s, with many reports of them attacking boats. One rumor claims that a man was fishing in his small motorboat when something large and dark, just under the water, was making huge ripples and splashes, started ramming the underside of his boat. The man was knocked out of his boat and frantically started swimming to the shore, with the creature following him from behind. Luckily, the creature suddenly swam away and the fisherman survived with only minor injuries.