My daughter wears a 13 1/2, so I ordered the 13/1. They are too big on her, giving too much room between the big toe and the tip of the shoe. I don't think it would stay on when wet. This happened with my boy's pair as well. He wears an 11 1/2 and the 11/12 were too big. My kids have wide feet, but that didn't seem to be an issue when trying them on. regards, Mrs. L.