Belfast Lough is a significant, sheltered sea lough on the east coast of Northern Ireland, forming a major inlet of the Irish Sea. It is a vital environmental and recreational resource, noted for its diverse marine habitats ranging from muddy seabeds in deeper waters to rich estuarine environments at its head. The lough serves as a popular sailing destination with substantial marinas and supports a variety of marine life, making it a destination for both recreational boaters and anglers.