Seal Beach is a coastal city in Orange County, California, United States. It was originally known as Bay City before it was incorporated into Oran…Seal Beach is a coastal city in Orange County, California, United States. It was originally known as Bay City before it was incorporated into Orange County under its current on October 24, 1911. As of the 2020 census, the population was 25,242, up from 24,168 at the 2010 census.