Skip anythign you have ever had including Teva's and go get a pair of Ecco's. They are a pretty penny, but they are the most comfortable I have found.
My flat footed self loves Teva's by the way (sailing, beach, waterpark, washing the car, etc..), but with flat feet in Charleston at the end of May my black Teva's where hot hot hot and not very comfortable. Popped into a shoe store and bought a pair of Ecco sandals and my feet were floating ( and still are).
If you are lucky enough to live near and Ecco outlet store they are about 40-60% of the retail, but they are worth it even at retail they are so comfortable. They are not all terrain like the Teva's however, just great day sandals.