Sex isn't frequent in the show. It's present at times, but usually only has a moderate impression. There's some implied adultery, and one scene of masturbation that doesn't have nudity but is suggestive.
Episode 1: Though the scene is comedic, there is a prolonged scene in which Skylar gives Walt a pitiful handjob (no nudity is depicted). Later in the episode, a woman's bare breasts are seen briefly, but clearly, through a second-story window shortly after Jesse exits the house through the same window. At the end of the episode, Walt arrives home late and kisses Skylar passionately. He turns her onto her side and enters her from behind, no nudity is depicted although the scene is quite explicit.
Episode 2: The episode opens immediately where the previous left off, Walt and Skyler are having sex. Heavy moaning is heard, and lots of thrusting is depicted, but the only nudity in the episode is Walt's bare buttocks as he leaves the bed to go into the bathroom.
Episode 3: There is a brief scene in which Jesse goes into a motel with a prostitute. The lights are out, so no nudity is clearly seen, but in silhouette we see Jesse sitting in a chair with his pants around his ankles and the prostitute dropping her panties. She sits atop him and, briefly, thrusting is seen.
Episode 7: In a school board meeting, Walt touches Skylar's crotch underneath the table. He rubs her crotch, she is clearly turned on. In the next scene, she rides him in the backseat of their car. A lot of thrusting is seen and moaning is heard, but no nudity is depicted.
Episode 1: Walt, in a confused state, shoves Skylar against the kitchen fridge and pulls her panties down, despite her protest. He is about to enter her when she screams at him to stop. He does and exits the room.
Episode 3: Walt's bare buttocks are seen while he is walking through a convince store nude.
Episode 13: A man is clearly seen having sex with a woman on the floor of a crack den. No nudity is shown, just heavy thrusting and moaning is heard.
Episode 4: Skyler is shown having sex with Ted. Moaning can be heard and thrusting can be seen, although in silhouette. We can see Skyler's reflection on the photo frames that the camera dolly through. Then cut to the aftermath of the sex and see Skyler dressing herself with her bra already on.
Episode 5:The episode begins with a scene in a strip club. Various topless women are seen in various provocative poses (i.e.: giving lap dances, being motor-boated, taking pictures). The scene goes on for several minutes. Although all the women are topless, some do wear pasties.
Episode 11: Andrea can be seen topless in the darkly lit shadow. She then puts her shirt on.
Episode 12: In a comedic montage sequence, a prostitue is seen going down on several people throughout the sequence in their vehicles. No nudity is shown. Later in the episode, Marie makes a bet whether Hank will get a boner by giving him a hand job, again no nudity is seen.
Episode 3: Hank was almost caught watching porn on television, only scantly clad women are seen on screen. Also, later in the episode, a man is having sex with a woman on the floor as Jesse returns to his house, no nudity is shown although thrusting is seen and light moaning can be heard.
Episode 4: A naked woman can be seen sleeping on top of the bed sheet. Only her profile is seen.
Episode 6: Walter and Skyler sleeps in bed together, out of focus they can be seen thrusting (briefly, a moan is heard as the scene cuts out). In the next scene, after the act, Skylar runs out of bed to close the bedroom door. Briefly, full-frontal nudity is shown from a distance and out of focus. Walt gets out of bed and walks to the bathroom, his bare buttocks are clearly seen.
Episode 2: The final scene of the episode it is heavily implied that Walt is about to have sex with her and she doesn't want to. Nothing sexual is depicted, it is only implied, but it is disturbing.
Occasional non-explicit sexual references and dialogue.
NOTE: Nudity is edited in the AMC version of the show, though not in the DVD/Blu-ray/Netflix edition. But, in the strip club scene, panties are still shown in the DVD/Blu-Ray/Netflix edition.
The Season Five, Part One DVD and Blu-Ray sets both feature a bonus scene for the season finale in the special features in which Jesse receives a delivery from Saul Goodman. Throughout the sequence there is a topless female stripper dancing on a table and around characters in the room.
Not very graphic throughout the whole series, but it is present.