De Niro's character as a kid (Scott Tiler) spies on a young Deborah (Jennifer Connelly) practising ballet. When she finishes she strips off, although you only see her from behind. Margherita Pace doubles as Jennifer's character for this scene.
A little later this same woman is having a bath, when the boy walks in and looks at her body. She invites him to put his hand into the water and touch her, which he does.