Try using a Rash Guard shirt that you wear under the suit. I normally use on by Oneil or Body Glove and they are mainly designed for surfers who suffer the same problems. It is similar in construction to a turtle neck but made out of special material for swimming.
Here is a link to give you some ideas, but I would lean toward the shirts with the higher collars because it needs to stick out of the top of the wetsuit for teh best effect.