The megamouth shark swims besides a diver, demonstrating how big she is and how unusual her face is. Sakana-kun, a professor emeritus and TV personality, says excitedly, “Wow. How cute she is. She swims very fluently and gracefully, against all my expectations.” (Video taken by Shingo Kuzutani and Kotaro Ebara)

TATEYAMA, Chiba Prefecture--An ultra-rare megamouth shark wandered into a fishing net off the coast here early on May 22, prompting celebrity expert "Sakana-kun" (Mr. Fish) to jump on the case to confirm its identity.

The deep-water shark, whose scientific name is Megachasma pelagios, was found in a net offshore from the Sunosaki lighthouse in Tateyama at around 4:30 a.m. Later the same day, Sakana-kun dived into the water in his trademark fish-shaped headdress to identify it.

“She has a round head and banner mouth, which are the distinctive features of a megamouth shark. I am sure she is one,” said Sakana-kun, who is a professor emeritus of the Tokyo University of Marine Science and Technology and an illustrator, as well as a TV star.

“My dream has come true. I could see her vigorously swimming,” he added excitedly.

The mysterious, majestic fish, which is female and about 5 to 6 meters long, is still gracefully swimming after being transferred to another place in the ocean in a cage.

The Asahi Shimbun’s photographers also went underwater to film the so-called “phantasmal fish” alive and swimming.

The species was first observed in Hawaii in 1976, and its detailed biology remains unknown except that they eat plankton, according to the Okinawa Churashima Foundation, which runs the Okinawa Churaumi Aquarium.

The species has been found in 110 cases worldwide including in Taiwan and the Philippines and about 20 cases across Japan, most of which died after being caught in nets, according to Kazuhiro Nakaya, a professor emeritus of Hokkaido University.

Nakaya added that it is very rare to record an individual swimming, and that no one in the world would be able to artificially rear the species.