A teenage boy (Daniel Radcliffe, 16) takes off his shirt (we see his bare chest) and climbs into a bathtub; the ghost of a girl plunges under the water and peeks into the water, presumably trying to see him nude.
Laura is taking a bath. Robert gets undressed and joins her. Rear nudity of Robert as he gets in, and full frontal of both him and Laura when they get out.
During a warm summer's day Sebastian takes a bath outside in the garden in an old bathtub (rear and front briefly seen as he turns around while standing).
Rear nudity of Pepe laying in the bathtub filled with red water, Jarl-Kulle suspects it's blood and Pepe would be dead, but his little brother was only cleaning himself from a "tomato sauce accident".