There are two registers of studies here: above are two studies of what appears to be the same substantial three-masted ship as it approaches, with a yacht to its right; below is the slight indication of a low coastline, with another yacht in the distance. In addition, there is a prominent sketch of a buoy at the bottom centre.
The yacht at the top right is similar to one on the far right of 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 which also includes a prominent buoy in the foreground. 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).