In this sequel to Class Two at the Zoo, students in Class Three are going to sea! The see dolphins, sea lions, flying fish, and an octopus that's all knotted up. What they don't see is the pirate ship sneaking up behind... Before the students can say "Arrr!" they're captured! That is, until their friends from the sea come to their aid. Can these creatures save Class Three before the pirates reach Treasure Island?