It's been a weird month of sunfish showing up in unexpected places.

Take, for instance, this impressive sunfish that was found at the mouth of the Murray River in South Australia last weekend.

Local Linette Grzelak uploaded a photo to Facebook, which shows off the creature's truly impressive size. 

10914936 3x2 700x467(Ralph Foster/iNaturalist/CC BY-NC 4.0)

Although massive, these odd-looking fish are harmless to humans. Their teeth are fused into a small beak, which they are unable to completely close. They use it to munch on jellyfish and zooplankton as they float around the oceans.

Sadly, the creature was already dead when it was found. According to a fish expert from the South Australian Museum, this particular species is pretty rare in South Australia.

"I've actually had a good look at it, we get three species here and this is actually the rarest one in South Australian waters," Ralph Foster told Camron Slessor at the ABC.

"It's the oceanic sunfish, which in other parts of the world is common but here it's more unusual, it's the one known as Mola mola."

M. mola, or the oceanic sunfish, is found across the world including America and Asia, although they normally stay within temperate or tropical waters, and keep their range farther out in the sea away from the coasts.

Even if you're aware of the existence of sunfish, their sheer size can still take you by surprise if you're lucky to encounter one. 

"A sunfish found by my partner along the Coorong a couple [of] nights ago… I thought it was fake," Grzelak said in a Facebook post.

This isn't even the first sunfish news we've had this month, though. A different type of sunfish recently landed on a beach in Santa Barbara, California.

That specimen, known as the hoodwinker sunfish (M. tecta) was even more interesting to biologists because the hoodwinker is thought to only live in the Southern Hemisphere.

body hoodwinker livingA hoodwinker sunfish photographed in 2017. (Explorasub, CC BY-SA 4.0)

As ScienceAlert writer Michelle Starr explained at the time, "most known specimens have turned up in the Southern Hemisphere, including the one from New Zealand which scientists used for the scientific description published in 2017. So naturally it was thought this enigmatic animal lives on the southern half of our globe."

"But the 2.1-metre (7-foot) Santa Barbara sunfish, which washed ashore at the Coal Oil Point Reserve, throws an interesting curveball into our understanding of these creatures."

There's plenty we still don't know about these enigmatic fish, but we can't undersetimate their ability to travel - the oceanic sunfish has been recorded swimming up to 26 kilometres (16 miles) in a day with a speed of 3.2 kilometres an hour (2 mph). Who knows where they'll turn up next.

You can check out more pictures of the fish on iNaturalist, where the find is attributed to Jacob Jones and Craig Tarry.