Cinematographer Robert Surtees (who had previously worked on classics like Ben Hur) was familiar with Nichols' style from Who's Afraid of Virginia Woolf? and was impressed by his far-out camera direction and inventive shots. An example of this is the famous scuba-diving sequence, where we see Ben's parents and their friends from Ben's perspective inside a scuba suit, before he jumps into the swimming pool. Later, we look up at his father from the bottom of the pool. It's an example of cinematography being used to say something about a character: he feels separate and isolated from everyone else. Nichols uses frequent shots through glass and water to emphasize Ben's alienation and isolation. (Source)

Other famous sequences include one that cuts between Benjamin drifting in his pool and staying in the hotel room with Mrs. Robinson, making it look like he's moving from one place to the next without any change in place or time. It conveys how his aimless drifting and his meaningless affair are totally related. Surprisingly, Nichols was a stranger to this kind of montage, but what he was aiming for was a dreamlike sequence—maybe all this was just a fantasy. He had to make the different sets look as similar as possible so the viewer wouldn't notice the transition from one to the other until it actually happened. (Source)