If it weren't for the sharks, the reef would be a tropical paradise underwater. In this second adventure, Pi and Cordelia are now parents of their new son Junior. And Pi's shark enemy, Troy, is again on the loose, on the hunt with his shark gang, and just waiting for high tide. Pi decides to train his family and reef buddies in the art of water fu to have them all prepared for the underwater battle. A mysterious new reef fish, Ronny, begins to distract the reef creatures with new ideas to protect the reef. However, the reef does not know that Ronny is Troy's spy. Things are at an all time low when Troy captures Cordelia! Now Pi and his son Junior not only have to save Cordelia, but to also save the reef and its motley school of fish and friends!