Water-based media is the material foundation of the watercolor language system. The fluidity of water, the transparency of pigment, and the texture of support interact to build the unique visual characteristics of watercolor. Contemporary watercolor creation continues to break through the inherent framework of traditional realistic narration and explore the beauty of texture, contingency, and artistic conception of water-based media. At the same time, in the process of material mixing, support innovation, and idea expression expansion, there are also some practical problems, such as vague ontology language, superficial media experiments, and unbalanced creation evaluation standards. Based on the ontology of water-based media, this paper clarifies the internal logic of aesthetic potential, rationally looks at the boundary changes brought by the expansion of media, and puts forward optimization paths from the aspects of deepening media cognition, rationally controlling the innovation scale, consolidating material knowledge, and connecting the spiritual connotation of media language, in order to realize the release of aesthetic potential and orderly expansion of the boundary of water-based media, and provide practical reference for the innovation of contemporary watercolor.