View this artwork by appointment, at Tate Britain's Prints and Drawings Rooms
The image is so faint that it is almost illegible, but it seems to show two ships, a distant three-master to the left, and a vessel closer in at the right, drawn with the page turned horizontally; waves appear to be breaking across the foreground.
The white gouache has been subject to oxidation. The leather stains on this sheet, corresponding to the folded edges of the overlaps inside the front cover, indicate that it was originally folio 1. See folio 18 recto (D04012) for comparable leather stains from the back cover.