Windsurfing is not all the same
One example: How is it possible that there are two world champions in the same discipline in one year?
The PWA World Cups establishes an international champion in Wave and in Freestyle. In the discipline Slalom, there can be more than one World Champion, because beneath the PWA (Slalom 42), the International Funboard Class Association IFCA also organizes contests (Slalom World Championships). The PWA Slalom World Champion 2008 is called Antoine Albeau and the IFCA-winner Ben van der Steen. In the discipline Racing, the International Raceboard Class chooses the best of the best. The International Speed Windsurfing Class (ISWC) finds out who is the fastest speedsurfer of the world.
Other competition classes like the International Mistral Class Organization, the RS:X class (Olympic class) the Techno 293 Championship or the Formula Windsurfing Class, which explicitely prescribe special equipment and regulations, also choose their respective World Champion. In the Techno Class, for example, it is only allowed to use a 293 One Design board.