Rio del Mar (From Spanish: Río del Mar, meaning River of the Sea) is a census-designated place (CDP) in Santa Cruz County, California, United States. The name "Rio Del Mar" was chosen as a "catchy" name to promote real estate in the area during the 1920s. There is no body of water by that name in Santa Cruz County. But there is a large creek, Aptos Creek, that goes through Rio del Mar and empties into the Monterey Bay at Rio del Mar. Aptos Creek is the "Rio" in Rio del Mar.