Hair: real hair looks semi-transparent at the ends (both ends btw) and tends to have a hi spec value, although with lower hardness.
Skin: yours does look rather to uniform. Real skin reacts differently to light as the fat below the skin varies along with the thickness of the skin. It also has a variety of wrinkles and streched areas that will discolour to red or a lighter shade of skin tone. And as she is in water wouldnt her skin be wet looking? higher reflect and hardness.
Water: I may suggest lots more smller surface ripples from the legs that are distrurbing the foreground.
wow very nice indeed! but the hair needs work…