OK... here it goes.
I should start off by saying in all of these, you did a great job exposing (sp?) the subject and getting sharp focuses.
#1 I seems to me that the subject is the guys face, correct? Centered composision usually doesn't work and I don't think it works here either. I also feel that the sail is also a sub focal point and if you were to crop this so that the dudes' face was lying on the bottom right third in a 2x3 crop ratio this shot has a lot of potential. You will probably find on here that a lot of people don't like selective coloring (me being one), but I feel in this particular case that is helping the comp.
#2 watch out where you point the camera. try not to cut off body parts in awkard places (try not to cut off at joints i.e. elbows, knees, shoulders etc.). This is a good excample of an awkard cut. Half of the shoulder, and only part of the top of her leg is showing. The horizon is not level and that is hurting this picture. For this one, it might have been better to have cut all the legs off up to say the middle of the waist, and have her whole left side (arm and all) showing. I do like how much open space is in front of her, but just the fact that she is cut in weird places kind of hurts this one.
#3 same as #2 as part of her butt and elbow are missing.
#4 This one could be improved (other than the fact that his left elbow is cut off) by cloning out the wire and bringing up the levels in his face.