A courier of the Maritime Postal Service, Santo, a cod fish, takes on a special assignment: to find the missing delivery. In his search, travelling from the North Pole to the South Pole, he learns about the variety of life in the ocean and its problems. Will Santo be able to save the reputation of the Maritime Postal service despite the nefarious efforts of the underwater criminals? It seems that the outcome of the age-old conflict between the Penguin Kingdom and the White Bear Empire hinges on the delivery of a sacred parcel.