We were in the Mediterranean last year for 2 weeks and did a tremendous amount of walking. (I did not gain one lb.!!!) I wore tennis shoes when I knew we were going to be walking on rocky surfaces, but most of the time I wore a good sandal I bought at Kohl's that had 4 strips of velcro closures across the top. I love them! Were not expensive. The best thing about them is being able to adjust the velcro at different places on your foot as our feel always swell when walking alot, especially in warmer weather!
I just returned from the Caribbean and wore the same shoes there.
The aqua shoes we bought were also great at the beach - snorkeling, etc.