You may need a cold-water dip after watching Ludivine Sagnier’s sizzling performance in ”Swimming Pool,” the English-language debut of director François Ozon. Set in the deceptively serene French countryside, the film tells about a demure British mystery writer (Charlotte Rampling) who escapes to her publisher’s summer home for a little inspiration. But when his provocative daughter (Sagnier) shows up unannounced, the prim novelist is sidetracked by the teen’s seedy conquests — an irritating distraction that grows progressively intriguing. Ozon blurs the line between fantasy and reality as he explores the increasing tension between the characters to create a chilling erotic thriller. EXTRAS Skippable: a ”Pool” trailer and a montage of deleted scenes as skimpy as Sagnier’s wardrobe.