This scale of wind speeds devised in 1805 by Sir Francis Beaufort is still in use today.
Crests have a glassy appearance.
Surface generally white. Wave heights quoted are approximately those that may be expected in the open sea. In enclosed waters the waves will be smaller and steeper. Fetch, depth, swell, heavy rain and tide will also affect their height, and there will also usually be a time lag between any increase in the wind and the consequent increase in the sea.