An American fisherman made a very rare discovery in the Indian Ocean -- a two-headed bull shark.

Christopher Johnson says he caught a pregnant bull shark that gave birth to the conjoined sharks.

Johnson took a photo of the creature and shared it with scientists, who explained that this occurs when an embryo doesn't split. 

It's the first time, however, that it's been seen in bull sharks.

The two-headed shark was given to researchers at Michigan State University.