I bought these for my son who wears an 8 - and bought an 8, in spite of the advice here suggesting otherwise.  He's never had any problem with any shoe, sandal OR water shoe - but he couldn't wear these at all.  Even after adjusting the 'laces' to the best of our ability, he said they hurt - and couldn't wear them, even in the unbearable heat of the water park.  He suffered all day in bare feet, rather than take a chance on the blisters that started to form after only a few minutes of wear.  They were NOT too large, nor too small - but extremely uncomfortable, and basically a loss of money for us.  We couldn't return them but we sure would never buy them again!  We'll be replacing them with the other ones (without the lace system).  We had also gotten a pair of the lace-free beach style (same brand), and they worked fine.