In my humble opinion:
My first impression is that you need much more light on the model in the first 3. The water in 1 and 3 looks nice and bright to me, which doesn't lead me to believe that they're under exposed, but that you needed some light coming from the front of your model. Number *2* looks under exposed to me.
#4's background is too busy for my liking and, as someone mentioned, you have a shadow running through her shirt.
You have a pole coming out of the guy's head in #5. It also looks to me as though it might be a *bit* underexposed.