As for their respective relationship statuses, Hudson is single. She called it quits with Bellamy at the end of 2014, and, sure, she's had an alleged tryst with Derek Hough since, but that wasn't much. Still, just because she's single doesn't mean she's ready to mingle.
Martin is reportedly still seeing Jennifer Lawrence, although they haven't been photographed together since January. He and Gwyneth Paltrow famously consciously uncoupled March 2014. (Still don't know what that is? Don't worry. Neither does Paltrow's mom, Blythe Danner.)
It's also worth noting that Hudson and Patlrow are longtime pals.
It's unlikely that Hudson would break Girl Code and hook up with her
friend's ex — especially since Paltrow and Martin are on good terms (see
also: their Valentine's Day beach trip
together or him throwing Gwyneth a birthday party). Hudson and Martin
were probably just catching up and enjoying the weather, as beautiful
friendly people who live near beautiful beaches do.