Watch
Step Into Liquid. There is a section about a group of chaps that surf the wake created by the supertankers.
Apparently they do a similar thing with cross-channel ferries near the isle of wight. At this windsurfing school (which is totally sheltered from groundswell), when the guys see the ferry disappearing around the headland, they remove the sails and paddle out to catch the wake that the boat leaves behind.