This sandal is a good 1.5 sizes too big...I normally wear a 39 in a European shoe. I ordered the 38 in this Gizeh and there's room to spare in the back, although not extremely so. The look is amusingly tray-ish.
The arch support is very good. These will be my indestructible wear-to-the- beach-and-get-wet sandals.
*Of course* I chose the red pair!