Water view is a room category that is about $20 more per night or something (I'm not exactly sure of the price difference). The area of the resort would be a request....and it won't be guaranteed. I do think they do what they can to honor requests but its not always possible. When we stayed at CSR we requested Cabanas and gave the two building numbers we preferred. We did get our request and got a great convenient room.
So if you want the water view I'd reserve that and make the request for Casitas.