This bizarre "giant swimming head" is about to return to Bali

Dive centres in Bali, Indonesia, are excited for the return of a regular visitor that looks like an underwater pancake and turns up each year when the water temperatures drop.

“The water temperatures are starting to drop around the island and that can only mean one thing: the molas are on their way!” says Scuba Junkie Penida on Instagram. 

In the post, the dive centre shares stunning footage taken by their dive instructor India Beaumont of a bumphead sunfish (Mola alexandrini) swimming slowly past the camera at Malibu dive site in Nusa Penida, Bali. 

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These huge fish can grow over three metres long, making them the largest bony fish on Earth. These weird animals “are truly one of a kind, as they resemble a giant swimming head with oversized fins,” the dive centre adds in a statement.

"Mola have a distinctive bullet-shaped, short body that ends abruptly in a thick rudderlike structure called a clavus which is just behind the tall triangular dorsal and anal fins. The development of the clavus results from the folding of the mola's back fin into its body as the fish grows.”

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These huge fish are harmless to humans and spend much of their time in the deep sea – so seeing one is an incredibly rare event for most recreational scuba divers.

"However, around Nusa Penida, during the months from July to October when the water temperatures drop, they rise to shallower waters, offering an unforgettable diving experience to be checked off your list,” says the dive centre. 

Image and video credit: India Beaumont & Scuba Junkie Penida

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