Every kid has seen the contrails that follow a jet tearing across the noon-time sky. That's what this is a picture of. Except that the trails in this picture are produced by SHIPS, not jets, and the image is taken looking down at the sea instead of up at the sky.
Ship's exhaust can cause the creation of stratus clouds which can be several miles wide. In this image, the gray bits are ship tracks, the blue bits are higher clouds, and the green is the coast of Washington state.