Episode one has some very strong references in a very comedic setting.
A couple have sex on a bed, the man thrusts and the woman moans. There is no nudity shown, though the scene is fairly graphic. The man removes a condom, we do not see this, however is is implied, as we see his bare buttocks.
Episode two also sees the main females, at a house party, wearing just a bikini. They dance in a hot tub.
There are some mild references to breasts in ep 2
In episode four there is one sex scene between a couple, not graphic at all. But it is in slow motion.