Agari

Agari-senpai, a big shark rumored to the model for the movie Jaws. He's a "senpai" to Wakasa because sharks are the top amongst fish. Although Agari-senpai looks scary, he's just shy. He hides underneath the water with only his fin visible because he's so shy. He's too nervous to speak because he ends up scaring people when he opens his mouth and flashes his many sharp teeth. So he uses body language to communicate instead.

(Source: shinkeikaku.wordpress.com)