LONDON - Hungary's Eva Risztov won a gripping Olympic women's swimming marathon by just 0.4 seconds on Thursday. The 26-year-old led for much of the race in the Serpentine lake but she touched only marginally ahead of America's Haley Anderson with a winning time of 1hr 57min 38.2sec. Italy's Martina Grimaldi took bronze and home favourite Keri-Anne Payne was fourth, with the top four separated by just four seconds. Risztov, 26, competed in the pool at the 2000 and 2004 Olympics before retiring in 2005, only to return to the sport as a marathon specialist in 2009.