A ghostly white lump of rotten flesh in the shape of a mermaid recently washed ashore on an island in Papua New Guinea — and experts baffled.

The strange sea creature was likely a marine mammal, but its exact origins are unclear, experts told Live Science.

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It is known as a globster — an unidentified organic mass that washes ashore. The origin of these mystery lumps is hard to pin down because much of the corpse has rotted away and most are missing body parts that have fallen off at sea. In this case, most of the creature’s head and large chunks of its flesh are missing.

There is no information on the size and weight of the corpse because it was not properly measured before locals buried it, NIO representatives told Live Science. And no one collected DNA samples, which makes a proper identification almost impossible.