Julie and Jeff have sex, exaggerated sounds are heard for an extended period of time (numerous), but they are not seen. They are seen after sex, he's wearing briefs, she's hidden by covers.
Sexual innuendo. Slang terms for sex.
Pam and Sam have sex under covers. They emerge from under the covers, he is wearing a thong bottom, her bare breasts are exposed. Later they take a shower, seen behind a translucent curtain, he backs up against the curtain which allows a pretty good look as his bare bottom.