If it weren't for the sharks, the reef would be a tropical underwater paradise. In this second adventure, Pi's shark enemy, Troy, is on the loose with his gang and waiting for high tide. Pi decides to train his family and reef buddies in the art of "water-fu" to prepare them for battle, when a mysterious new fish, Ronny, begins to distract them. However, the reef doesn't know that Ronny is Troy's spy... and things are at an all-time low when Troy captures Pi's wife Cordelia! Now, Pi and his son Junior have lots to do to save her, the reef and its motley school of fish and friends!