Michelle Borth and Ian Somerhalder share the most intimate and explicit scenes in the show. Ian's erect penis and testicles are visible for a moment during vaginal intercourse, and Michelle's boobs, buttocks and shaved vagina are shown explicitly in multiple scenes. Seriously about as realistic as it gets as some angles show clear vaginal penetration taking place.
It is not a real penis that is stroked until conditioner squirts out. Per commentary.
Michelle denies penetration during commentary and interviews stating how good of an actress she is.
Very graphic sex scenes featuring full frontal male and female nudity, breasts, vaginas, butts, pubic hair, penises, and testicles are visible at times. This includes graphic depictions of intercourse, masturbation, and oral sex. The series centers around the sex life of a few couples, and there is frequent sex and sexual dialogue.
One particular scene involves a man ejaculating while his wife manually pleasures him by masturbating his erect penis.