3x15 Walk On Water
Derek finds Meredith in her tub, completely under the water, and pulls her out. She tells him she doesn't need rescuing. But he knows she's melancholy after the hurtful things her mother said to her when she was lucid and is afraid she was trying to drown herself. Meredith asks Izzie why she can't just believe in "happily ever after" and Izzie says she doesn't know what to believe in herself anymore.
Burke, Mark and Derek are amused to see that the Chief has dyed his hair now that he's single again. Addison comes to his defense and tells them all to leave him be, then confesses that she dyed her hair blonde after Derek left her the first time.