Zeus is a dog who follows a neighbor, a marine biologist named Mary Beth (Kathleen Quinlan), to work one day. Aboard a ship, the dog meets Roxanne, a dolphin that Mary Beth is studying. When she sees the dog riding on the dolphin's back, she decides to study their friendship. A villainous fellow researcher, Claude (Arnold Vosloo), tries to steal her research, but he is thwarted by the dolphin, the dog, and the dog's young owner, Jordan (Miko Hughes). Terry (Steve Guttenberg), Jordan's father, is a songwriter who still pines for his dead wife. Jordan, together with Mary Beth's daughters, try to ignite a romance between their parents, who are both unattached.