I have added screencaptures of Life Under Water, released 1989 and co-starring Sarah Jessica Parker and Joanna Gleason.
A dark comedy about five characters whose lives interweave late one summer in the Hamptons of Long Island. Kip is a bored and frustrated 20-year-old boy trying to break ties with his divorced mother Jinx, who is having an affair with Hank, a married man. Upset by this relationship, Kip decides to leave home, but only gets a few miles down the beach where he is taken in by Amy-Beth and Amy-Joy. A strange triangle develops between the three young people. Meanwhile, Hank and Jinx’s relationship dissolves.
You can view the screencaptures here: Life Under Water Screencaptures