The Mutation

The Mutation, the 36th book in the Animorphs series by K.A. Applegate, follows Marco and the Animorphs as they confront powerful mutations and uncover mysteries beneath the sea. While visiting an underwater civilization that could be Atlantis, they must also thwart Visser Three's plan to acquire a hidden Pemalite ship with advanced technology and complete Earth's invasion. The stakes are high as they struggle to safeguard both the mysterious underwater world and their own planet from the Yeerks.