Because of Amazon's/Crocs sizing questionnaire, I bought a half size higher than usual, and the sandals fit like flippers. They would otherwise be well cushioned and comfortable at the right fit.

When I called Amaxon CS to see if I could exchange sizes for a 10, I was told that I would have to pay for the return and that I would lose my prime discount for the replacement pair.

Really helpful. (?)

So I contacted Crocs who offered a full immediate exchange -- overnight. They're a company from whom I'd buy again directly.

The new 10M's are cushy and well designed for wear in rain or moist conditions. The insoles have tiny nibs to preempt slippage of the foot in the shoe, though if sized and strapped properly this should not occur. The nibs feel rough at first,. But break-in should occur in a week or two of frequent, but not daily, use.

I would suggest a gradual break-in in avoid hot spots or blisters. Both seem possible since these are not hiking sandals and the insole materials are fairly stiff. For hiking sandals,  go to Chacos for the best designed products. Crocs has a promising water sandal, however, in these Swiftwater River shoes.

They are generally true to size, given the 1/4 inch raised border around the outer insole, and perform as advertised. Future editions should soften the inner sole. If Crocs does that, they will achieve more five star ratings here.