The description of the "aspidochelone," probably a whale, in this medieval bestiary is a fantastic concoction of nature and legend, all in the service of Christian teaching. One characteristic of the large sea creature noted in the bestiary is its propensity to remain motionless for long periods of time with its back just above the water line, fooling sailors into believing it is an island. Later, as the text relates, when the sailors pitch camp on its back and light their campfires, the monster feels the heat and plunges suddenly into the watery depths. The whale is thereby understood allegorically as the wily devil who deceives sinners, ultimately plunging them into the fires of Hell.
The artist of the miniature focused on the dramatic moment of realization. While the sailors' broad faces express fear, one victim tumbles over with acrobatic flair and another man clings tenuously to the boat. To suggest movement, the artist set up a play of related curves and angles throughout the composition: for example, the improbably curved left arm of the man clinging to the boat echoes the arc of the wind-filled sail, and his legs conform to the diagonal of the mast.