A 'ghost' island that suddenly appeared in the Caspian Sea in early 2023 is playing a centuries-long game of peekaboo with scientists, and it's about to vanish once again – if it hasn't already slipped beneath the waves.

The island is located at the tip of the Kumani bank mud volcano, located underwater off the coast of Azerbaijan. On random occasions, when this volcano blows, an island of mud breaks through the waves and reforms about 20 kilometers (12.4 miles) from the mainland.

The temporary land mass was first documented in May 1861. But the next year, it was gone.

In the 20th century, the island came and went at least six further times, according to records. In fact, the blob of land rarely sticks around for longer than two years, before slipping beneath the waves.