• Yoji Ookata/NHK/teletechnology/youtube
    1 of 8

    We've heard of crop circles, but sea circles? According to Reef Builders, a diver discovered these carefully crafted pieces of underwater art off the coast of Japan.

  • Yoji Ookata/NHK/teletechnology/youtube
    2 of 8

    Diver Yoji Ookata originally thought the 6-foot-wide decoration was coral, but found it to be a sand formation once he got closer. Befuddled by what created the design, and doubtful of human involvement, Ookata decided to take a few pictures and come back the next day. 

  • Yoji Ookata/NHK/teletechnology/youtube
    3 of 8

    The next day, Ookata caught the artist at work. A small pufferfish was using his fins to wriggle his way through the sand, leaving the design behind him. 

  • Yoji Ookata/NHK/teletechnology/youtube
    4 of 8

    The small, silvery pufferfish made these amazing sea circles to attract a mate. The male uses his pectoral fin as a carving tools to shape the sand in pleasing patterns for females to admire. 

  • Yoji Ookata/NHK/teletechnology/youtube
    5 of 8

    The pufferfish's creations are not a one-time effort. To ensure that females see the design, the male has to constantly fix the piece so it doesn't fade due to water flow. 

  • Yoji Ookata/NHK/teletechnology/youtube
    6 of 8

    Of course, the more elaborate the sand design, the more ladies the fish is likely to attract.

  • Yoji Ookata/NHK/teletechnology/youtube
    7 of 8

    Once the fish finds his mate, the pair lay their eggs in the center of the of the ring. Researchers believe the sea creatures do this because the ring's ridges help bring water flow to the eggs in the center. 

  • Yoji Ookata/NHK/teletechnology/youtube
    8 of 8
    Next: More Freaky Undersea Creatures

    These amazing creations are just another reminder of how much we still have to learn and discover about our world.