The actors were initially linked romantically in May (15), when they were first spotted holding hands in New York at a Met Gala afterparty, and although they have yet to comment on the relationship speculation, they no longer appear to be hiding their affection for one another.
Mara and Bell, who were both wearing swimsuits, were photographed walking along a beach on Thursday (03Sep15) with their arms wrapped around each other as the Brit walked the former House of Cards star's Boston terrier by the water.
An onlooker tells People.com, "They 100 per cent looked like they were a couple. They had their arms around one another the whole time and they looked totally in love."
Mara previously dated another Brit, fellow actor Max Minghella, on and off for four years before calling time on their romance last year (14), while Bell also split from wife Evan Rachel Wood - the mother of his two-year-old son - in 2014 after less than two years of marriage.