Chose the school based on your major. That is how you will earn your living. Water polo and good grades give you options to maximize the number of schools you can attend.
Do you need to play all 4 years? Can you wait and work really hard for 2 years and then play?
What is the culture of the team?
How important is winning to you? Can you deal with having a losing record but having a great experience?
What do players on the team think about their experience?
Things like class size, school ranking, if you like the campus (food, buildings, dorms, off campus living, immediate area activities, etc.) all should be a part of your individual matrix.