The invention provides seed and plants of the watermelon line designated WAS-45-2158S. The invention thus relates to the plants, seeds and tissue cultures of watermelon line WAS-45-2158S, and to methods for producing a watermelon plant produced by crossing a plant of watermelon line WAS-45-2158S with itself or with another watermelon plant, such as a plant of another line. The invention further relates to seeds and plants produced by such crossing. The invention further relates to parts of a plant of watermelon line WAS-45-2158S, including the fruits and gametes of such plants.
