Photographer and Boing Boing reader Craig Berry contributed this photo to the BB Flickr Pool. He shot this near Point Dume in Southern California, and explains:
The boat's name was Zeus. When I first arrived the tide was coming in and only the "S" was visible. As the tide continued to rise I saw the "Z" and "E". The water would rush up and collect in the stern and then as it washed back out it created this whirlpool effect.