These boots are made for diving. They are made to be worn under rocket fins. A combat diver can wear his rocket fins with these boots filling the role of booties on a dive mission. Once he arrives on the beach the fins can easily be removed and he has foot wear ( more rugged then booties) to run around in. The options a diver had before these was booties or chuck taylors. These have key design features for marintine use and finning. They are not made to fill the role of a combat boot.
Yes..I am a size 11 and I needed a size 12. It was a bit tight in the front at 11. It got comfy when I removed the thick inside Dr Sole like sole in it. Plenty of space after removing that.
I would say they fit like chucks. But they fit fine for me. Granted my left foot is a size 11 and my right is a size 9. So... they fit as well as expected with one shoe being 2 sizes too big lol.