Blue seventy also makes a pair that I think are pretty nice http://www.blueseventy.com/products/acc-blueseventy.html
Surf booties area also very nice and warm as well.

They work great for training, but if you're racing in cold water, make sure and check with the race before wear them, as they are generally under illegal equipment in most USAT races (although some may grant cold water exceptions), they fall under the 'webbed feet' category of aid.