Jinmen Gyo introduces itself by scaring all the other fish in the background and breaking the glass, flooding the room the player is in. Its attacks involve it jumping across the room in an arc with its mouth open. Another is him jumping up from below a platform, with bubbling as a warning sign. Another is him going in from the side and eating the platforms, which move into its mouth. All of the attacks involve an open mouth the player can shoot into, although the third attack provides the best opportunity.
After being shot enough, it does the second attack one last time but in the center platform, with its green blood being the indicator. After that last attempt, it lays there, flopping; the player can even stand on its body at that moment.