There appear to be two studies here, one above the other and inverted relative to the sketchbook’s foliation. Each shows a small building, perhaps a tower, at the left, with clouds above the horizon of the sea beyond. Each also shows a small disk just over the horizon, presumably indicating the sun rising or setting, or possibly the moon. Turner’s annotation indicates the viewpoint is a beach at ‘low tide’.
There are various studies of fishermen, fish markets and coastal views in the sketchbook, particularly on adjacent pages at this end, as set out in the Introduction.