Hi to all! 
I’m trying to reproduce this style render
www.gruppomelissa.com/ispirazione.jpg
Now my work is this one
www.gruppomelissa.com/06.jpg
The sea is quite different. More contrast… for exemple!
Thanks in advace! 
Seems like you have a very good start in the render.
To get more contrast in the water I think you need to have it reflect more of the bright sky + you need some darker objects to be reflected in the water. That way you will extend the key extremes a bit. There aren’t any dark objects reflected in the water as it is now.
Good Job! and good luck with the final!
The key to this image is a good skyimage for skylight and some photoshop tweaking …nothing special at all.
The skyimage is from a overcasted sky.