#1 would be an interesting shot given the right light, but during midday, it's just too harsh given the water there isn't a deep aqua blue like in #3.
#2 again would be more interesting at sunrise or sunset depending light direction. I've found that sometimes images taken during midday make good b&w. Maybe a touch overexposed, and I'd clone out the bouys. Just not a very interesting composition overall for me. Interesting looking tree, but can't seen enough detail.
#3 has a nice color pallette and I like the repeating pattern of the jetskis. A different composition without the objects to the left would be better I think. They don't seem to be related to the subject.
#4... The silhouettes are just too complicated. Simplify so each object is easily discernible from every other object and identifiable. The one chair in the center does stand out, but I'm more interested in the umbrella because it is more directly tied to the typical paradise beach scene. Simplify.