People have often told me that ear plugs keep you warmer in cold water. The idea is that the cold water hitting your ear drum makes you much colder than if you avoid this. It didn't seem all that believable to me. But I decided to give it a try, as I've been having a hard time swimming with my face in the water. I get "ice cream" headaches, and therefore revert to head up breaststroke.
So I used some old silicone ear plugs I had sitting around. I hate how they muffle all sounds. BUT, I was much warmer. My toes didn't get cold. And I was able to do my longest Alki swim to date with my face in the water most of the time. So perhaps it makes a difference. I will have to try the earplugs that advertise they preserve the ability to hear.