Raw, peeled potatoes can sit in water overnight. It is a trick cooks use to prepare potatoes the night before for cooking the next day.
Covering potatoes with water prevents them from turning brown, which can be unsightly. The potatoes also need to be refrigerated to keep overnight. Martha Stewart suggests scrubbing the potatoes under cool water, and then peeling them. Next, she recommends cutting them up as directed by the recipe, and then placing them in one-inch of cold water. Cooks can also add a small amount of lemon juice or salt to the water to keep potatoes fresh.