He competed for Germany at the 2004 Summer Olympics in the 1500 m freestyle, where he missed the final, but returned to the 2008 Summer Olympics, where he won a bronze medal in the 10 km open water race.[1] At the 2012 Summer Olympics, he finished one place higher, claiming the silver medal.[2] He was the world champion in the 10 km open-water swimming event in 2004, 2006 and 2009. From to 2005 to 2011, he won gold in the 5 km event seven times in a row. He was jointly awarded the inaugural Open Water Swimmer of the Year by Swimming World Magazine with Chip Peterson, winning following titles in 2006 and 2009 alone and 2011 together with Spyridon Gianniotis.