Boat covers have many uses. First and foremost, they help keep your boat clean. Waterproof boat covers will repel rain and moisture, prevent mold or mildew from growing on the interior of your boat. A cover will also defend against bird droppings, tree sap, falling leaves and other dirt and grime. Boat covers with UV protection will deflect harmful UV rays from the sun. Prolonged sun exposure can fade your boat’s paint and cause unwanted cracks.