I ordered this swim top initially in a size S (8-10), I followed the size chart exactly and I am usually a size small in tops from L&Y anyway. It arrived and it was so tight I could barely get it on and it was really squeezing my rib-cage. I also had my friend, who is a size smaller than me, try it on and she said it was uncomfortably tight as well . It was so small I wondered if the top was a size XS (4-6) that had been labelled wrong.
I re-ordered the top in size M (12-14) and luckily that one fits a lot better and I can actually move and breathe in it. The top itself is nice quality and I love the design, but I would say it runs small and would recommend sizing up.