Mystery behind underwater 'crop circles'

Divers were stumped by these strange patterns first discovered off the coast of Japan in 1995... until they caught the culprit red-handed years later.

A photographer captured the photos while on a dive near Amami Oshima at the southern tip of Japan. The rippling geometric sand patterns, almost 80ft below sea level, were estimated to be nearly 6ft in diameter.

A TV crew carried out a study of the mysterious underwater circles and found that the 'artist' was a small puffer fish which, using only its flapping fin, tirelessly worked day and night to carve the circular ridges.

It is designed to attract female puffer fish. After mating, they lay eggs in the centre of the undersea circles.

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