24 x 36 inches
The strength of this image is largely due to the large tonal range. The waves at the bottom are almost black, while the sail on the left is pure white. Tonal contrast is much less in the background, giving a sense of distance. I've noticed that a lot of artists try to get dark shadows in the corners of a composition. This makes them crisper (unless, of course, seen again a very dark wall or frame, which is unusual).