Keep in mind that it can be very hot. Even the coolest looking hat doesn't look good if you are dripping sweat from under the brim.
My husband is a hat junkie. What he prefers for cruises is a tropical hat (I don't know the name of the style). It has a flat crown, with a band of mesh around it below the crown, then a wide, flat brim. It is made out of cloth and the mesh lets air in. It is also very easy to take with you in ports, since it will lie flat or can be folded up.
If you want, PM me and I will send you the name of the online company that sells them.