After browsing the internet, asking seasoned parents, and looking at social media forums, it seems the resounding answer to this question is a Classic Lined Croc.
Many of the swimmers love that they are easy to take on and off and they have some warmth to them. They dry fairly quickly and are light. A favorite among the girls.
My son, on the other hand, prefers to wear some sort of rubber slide with no padding. Several of the ones on the market have a fabric cushion under the strap. I would avoid this if possible.
Under Armour and Nike make a few versions that we have used in the past. He likes to use these all year round.
In short, your swimmer will want something that is light, easy to take on and off, and dries quickly.
An added layer of warmth in the winter is surely a bonus!
