Once you get past the initial disappointment of “A Bigger Splash” not being the long-awaited sequel to “Splash,” it’s a well-crafted piece of understated adult drama. Directed by Luca Guadagnino (“I Am Love”) as a loose remake of the 1969 French film “La Piscine,” it’s built around a steamy mixture of jealousy and miscommunication among lovers and former lovers, all set on a picturesque Italian island that is a playground for attractive, wealthy people. As is often the case with movies about the upper crust, we grow increasingly less envious of them as the story progresses.