I've been ordering this style sandal for both of my kids for years.  I struggle to get the right fit with their sizing.  This year was no exception.  My son is 10 years old and wears a size 6 shoe.  We ordered size 6 in the Blue Depths color.  His toes didn't come close to reaching the end and there was quite a bit of space around the outside of his foot, even for his slightly wider than normal foot.  In order to cinch the shoe down tight enough, he had to pull the cinch string very far out, which left too much string out visibly.  The velcro didn't come close to being tight enough around the top of his foot.  The fit on these is way off.  My son never has trouble with shoes being too wide and these definitely were both too wide and too long.  We didn't even attempt to send them back for an exchange.  I wouldn't have known what size to order that would have made these fit properly.