The Sundance Film Festival is in full swing, which means that celebs such as Jessica Biel, Naomi Watts, and James Franco have been traipsing around Park City, Utah, in cute hats and fuzzy sweaters. On Saturday, director Liz W. Garcia and actress Kristen Bell debuted their movie “The Lifeguard,’’ which will screen at the Coolidge Corner Theatre next week as part of theSundance USA program. Garcia will be in town to answer questions. “The Lifeguard’’ is about a reporter who returns to her Connecticut hometown and has a relationship with a teenage boy. Monday will also be a big day for Massachusetts at Sundance when the festival premieres the locally made Steve Carell drama “The Way, Way Back,’’ which was co-written and directed by Mass. man Nat Faxon.