Long periods underwater or exposure to running water can make the scabs or softened new skin fall off. This prolongs the healing process. Immersion in cold water for more than a minute or two slows down blood flow, which in turn slows down scar healing.
I have used ScarFade following the removal of a basal cell carcinoma in the middle of my forehead. My two inch scar has dramatically improved over this 3 month post-operative period and is barely visible. ScarFade is a wonderful product.