Winter's surrogate mother, the very elderly dolphin Panama, has passed away, leaving Winter without the only poolmate she has ever known. However, the loss of Panama may have even greater repercussions for Winter, who, according to USDA regulations, cannot be housed alone, as dolphins' social behavior requires them to be paired with other dolphins. Time is running out to find a companion for her before the team at Clearwater loses their beloved Winter...

At the aquarium where her father works, a teenage student meets a pair of mysterious boys who were raised by dugongs and becomes involved in the mystery of the worldwide disappearance of the ocean's fish.