Lala hosts a water-tasting event to expand her friends’ horizons, but the evening quickly devolves into a battle of exes when Schwartz confronts Katie for her recent hookup. Ariana takes Sandoval to task for an irresponsible mishap. James draws a literal line in the sand during a trip to the beach. Tensions boil over when Tom and Ariana clash about long-simmering resentments.