Sadly decreased Sunfish. Seen by local fisho the previous day floundering in shallow water, but the region is too dangerous to enter. Another fisho said he'd seen them washed up before. He'd lived here over 50 years.
Measured at 2.7m x 2.2m

From https://articles.listnr.com/news/giant-sunfish-washes-up-on-south-australian-beach/

"According to Ralph Foster, fish collection manager at the SA Museum, sunfish are known to bask in the sun’s rays at the ocean’s surface before diving hundreds of metres below to feed on jellyfish.

“You can tell it’s a bump-head sunfish rather than one of the other two types (Mola tecta, the Hoodwinker sunfish and Mola mola, the Ocean sunfish) because of the prominent chin you can see in the photo,” a spokesperson for the museum said."

Edit// added photos from two weeks later. Very smelly 😞