Towards the top left is a study of a heavy sea with colour notes and slight indications of masts and a coastline beyond. Compare the state and colouring of the sea in the painting East Cowes Castle, the Seat of J. Nash, Esq.; the Regatta Beating to Windward, exhibited at the Royal Academy in 1828 (Indianapolis Museum of Art).1 At the top and bottom are profiles of low coastlines, probably around the Isle of Wight.
There are also schematic studies of yachts under sail, made with the page turned vertically each way. For more on studies in this sketchbook relating to the regatta events at Cowes from late July 1827 onwards, see the sketchbook Introduction.
Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed., New Haven and London 1984, p.150 no.242, pl.246 (colour).