Situated 2km east of Swords and 1km northwest of Malahide. A large (280ha) artificial lagoon formed behind a coastal embankment carrying a railway line (Maps 1 & 2), ranging in salinity at the time of sampling (18-21/9/03) from almost fresh (1.2 psu) at the inner most part, up to 32.6 psu near the tidal inlet.