I tried these out down in Fla. - they keep your feet warm enough - 3mm - have a protective sole- lite weight and they keep the sand and coral out - they are discontinuing these - get some now - great for year round down there - great for summers in north east. I gave a pair to a friend in Fla. while I was down there and he just told me they worked great. Can't beat the price either - I just ordered 2 more pair for the future.
http://www.nrsweb.com/shop/product.asp?pfid=52343&deptid=1141#
http://www.nrsweb.com/shop/product.asp?pfid=52343&deptid=1141#