The unusual fish are often mistaken as sharks due to their upwards fin. They can grow to weigh up to 2.5 tonnes and are considered a delicacy in some parts of Asia.
Beachgoers were left stunned when a huge alien-like creature was washed up on the shore.
The unusual 6ft beast shocked tourists after waves carried it onto land over the weekend.
Tourists found the freakish creature, known as an “ocean sunfish”, as it lay dead on the sand.
The enormous grey and white fish is thought to have measured around two metres in length.
That is actually considered small for the species.
Cath Rampton and her husband Tom, who are vets, spotted the fish at the mouth of the Kennett River on Victoria’s south-west coast in Australia on Saturday.
Cath told Daily Mail Australia: “My understanding is it’s not a very big specimen, I think they can get up to double that size.”
And tourists Tim Rothman and James Barham found the fish on Monday.
“We were walking along and saw this big lump on the sand”, Mr Rothman told the Geelong Advertiser.
“I’ve never seen anything like that before. It looked like an alien from a distance.”
The fish was snapped as it lay on the beach with its flippers partially submerged by the wet sand.
It lay on its side, displaying a grey and white torso that has signs of scars.
And in another picture it appears to have red blood stains underneath its fin.
In the wild sunfish can grow up to 3m long, 4.2m high and weigh up to 2.5 tonnes.
The striking creatures are considered rare by experts.
But it is not uncommon for them to get washed up onto shores.
Another sunfish was found by fishermen last year at the mouth of the River Murray, also in Australia.
That beast weighed in at several hundred kilograms and measured 2.5m in length.
National Parks and Wildlife Service South Australia posted on social media about the unusual find.
They wrote: “Our Park of the Month at Coorong National Park served up an unusual surprise for two fishers on the weekend – a sunfish that washed up on to the beach. These huge beauties are the world’s largest bony fish and can weigh more than a car.”
The unusual looking creatures are usually found in tropical waters.
They are often confused as being sharks because of their upwards fin and are considered a delicacy in some parts of Asia.
Ralph Foster, the fish collection manager at the South Australian Museum, previously explained why so many sunfish get washed up on the beach.
“One of the big dangers would being hit by big boats at sea. They often eat plastic bags thinking they are jelly fish which can kill them.”