Haikouichthys is a green eel-like fish found in Dinosaur Island encountered before the Arandaspis. It takes one slicing power to kill and drops nineteen coins. It may take more hits if not using the Muramasa Blade or Kusangi-No-Dynamito. Sometimes, these fish may swim around while Otoro waits for a signal to start fishing. Once he starts fishing, all fish swim away as fast as possible.

A Haikouichthys with and Arandaspis and Opabinia as Otoro sits on his boat.