Timelapse footage of a sea of clouds. The resemblance of the cloud layer to the surface of the sea is not coincidental, as both are shaped by gravity waves, here in the inversion layer in which the cloud occurs. In 2009, the Cloud Appreciation Society petitioned the World Meteorological Society to recognize a new variety of stratiform clouds - undulatus asperatus, meaning roughened. Filmed in Colorado, USA, in summer.