Corresponds to standard shoe size. Light. I've worn them in the sea and the sole was thick enough to protect my feet from sharp projectiles etc. The adjustable straps are great and they never slipped off. I clicked in too and nothing hit them, not even sand. Comfortable to wear out of the water too - they are supportive, unlike the basic/cheap water shoes that have in the past caused me to have arch pains when walking on dry land. Definitely recommend.