I would say that what you are seeing is waves on the lake with the white caps showing as white specks you can go back in time with google earth and the lake may be calm and not look the same. The icon that looks like a blue earth that is historical imagery will let you see pictures of earlier pictures. Remember these pictures are only taken every so often and are not present day or time pictures. This is just what I know about this and many more people can tell you more about google earth.