I have never worn anything on my feet while swimming, except for occasionally wearing flippers, so I thought this would be a little odd, and I was right. They are basically neoprene socks that fit very well when wet, which I guess means they are doing their job. I did not race in the swim socks; I believe that they are only allowed in races when the water temperature is too cold. I did open water swim with them when the air temperature was in the mid to low 60s and so was the water temperature. They are really nice for the walk to the water, especially if the walk involves going on cold, wet sand and/or grass. They keep your feet nice and warm. They also have a textured sole which I believe keeps them from being less slippery. Swimming with them is the odd part, they do keep your feet nice and warm, but it felt like I was swimming with wet socks on. They also felt like they were going to slip off, which they never came close to doing, they stayed on perfectly. I didn’t kick much with them on, owing to a stress fracture I have, but kicking did feel strange. Since I did not kick, they were useful keeping my feet warm in the water. I can definitely say that swimming in cold water with these on is very nice, they do keep your feet warm. I did Escape from Alcatraz last year and these would have been very nice. My feet were numb and it made the long run to the transition area even longer. I would definitely pick-up a pair if you do cold water swimming.