This very slight outline is difficult to interpret. There are two figures, one pulling or pushing something. Possibly this is a rough idea for the man poling a punt to left of centre in Walton Bridges exhibited ?1807 (National Gallery of Victoria, Melbourne),1 for which a drawing is on folio 5 verso of this sketchbook (D05852). For other drawings in the book made around Walton see note to folio 4 (D05849).
Martin Butlin and Evelyn Joll, The Paintings of J.M.W. Turner, revised ed., New Have and London 1984., p.50 no.63 (pl.71).