Claus started in the Optimist dinghy, and later in the Europe dinghy participating in the world championship. After the Europe dinghy, Claus changed from Dinghys to keelboats and began racing in the Yngling class and won the world championship in 2002. He also sailed the Dragon class from 1992, and won his first world championship in Martinique in 1999, beating no more than 7 Olympic gold medalists, and the Danish elite of Jesper Bank, Poul Ricahrd Høj Jensen, Valdemar Bandolowski, and Theis Palm. Claus began competing in the H-Boat in 2006 and won his first world championship later in 2008. After that, he has been dominant in the H-Boat class, with no less than 11 world championships in the class.