German swimmer Hannah Stockbauer, the winner of five world titles, announced on Sunday that she was retiring from the sport at the age of 23. Stockbauer won the world crown in the 800m and 1500m freestyle at Fukuoka in 2002 and then added the 400m, 800m and 1500 in Barcelona in the following year. "I will not return. My decision is final," she told the Nurnberger Nachrichten newspaper. Stockbauer endured a disappointing Olympics in Athens in 2004 where she started as favorite in the 400m and 800m free but came home with just a bronze from the 4x200m relay.