Some say we're a nation of swimmers. And while the iconic image of a bronzed lifesaver at Bondi Beach has endured as a symbol of national identity, Australia's contemporary relationship to swimming is far more complex and varied. While some of us devote our leisure time to water-based activities, and cold water swimming groups continue to attract huge interest, one in four adult Australians are either a weak swimmer or can't swim at all, according to Royal Life Saving Australia.    So what is our relationship to swimming? How has it changed over the years? And what benefits does swimming offer us that other leisure activities don't?