Swains Lake (also known as Union Lake ) is a 341 acre water body located in Strafford County in eastern New Hampshire, United States, in the town of Barrington. Water from Swains Lake flows via the Bellamy River to the Piscataqua River estuary. A boat launch is available off Young Road. During the spring and summer it is a popular boating destination, while the ice of the colder months connects several snowmobile paths. The lake is classified as a warmwater fishery, with observed species including largemouth bass, chain pickerel, horned pout, and bluegill.