In analog or digital one can add vivdness by using selective/random dodging and burning. In this case, I burned the edges of the picture all around; it adds a certain compactness to the picture and the slight vignetting gives it an old feel. Then I go and burn the mids and shadows of the skies/clouds, followed by a dodge of the highlights. This makes the clouds very intense and 3d. In the end I add some almost random dodges (in this case along the surf). This adds more vividness, almost like sunspots.

Below you can see the picture before all the doging and burning. The difference is subtle; it just adds a bit of impressonistic feel.