Two greedy and boastful whales, Fifi and Fofo, decide to compete by eating as much as they can in one day and then meet at sunset to review their consumption. Thus, the two ungrateful friends engage in an unprecedented unrestrained marine feast, swallowing boats with fishermen, eating small ships with cheerful sailors, and devouring pirate schooners with captive princesses. While the two fanciful whales try to settle their differences, readers learn multiplication and division, and by the end of the book, they are able to calculate with remarkable precision how many legs eight octopuses have and how three whales can share six seahorses with bow ties and twelve shipwrecked harlequins.