Two gluttonous and boastful whales, Fifi and Fofó, decide to compete by eating as much as they can in one day, and at sunset, they meet to tally up their consumption. Thus, the two sworn frenemies engage in an unprecedented, unrestrained maritime feast, swallowing boats with fishermen, eating caiques with cheerful sailors, and devouring pirate schooners with captive princesses. While the two conceited whales settle their differences, readers learn multiplication and division and, by the end of the book, are able to calculate with remarkable precision how many legs eight octopuses have and how three whales can share six bow-tied seahorses and twelve shipwrecked harlequins among themselves.