Four young animal friends join the crew of The Tumblegum - the last remaining Beast Navy Submarine in the war against aliens taking over the world's whales. Beasts of the world are working alone until two human 'Callers' who talk to animals appear to drag humans into the fight. Continuing on from their adventures in book one (Yamba's Army), Yamba the pygmy possum, Bathurst the wombat, Albury science platypus and Bega the weapons bandicoot take the battle to the high seas, and an epic showdown off the coast of Japan.
