Skin deep
Superficiality. Not being able to get to know someone for real.
My date yesterday was terrible, he only talked about his job and the weather basically - he was so skin deep.
Deep skin docking
deep skin docking is essentialy the deepthroat action of docking, where the foreskin of one males penis completely engulfes the penis of another male.
I was surprised by how stretchy his foreskin was when he decided to perform deep skin docking on me during our fifth intimate docking session of the day.