The molecular structure of sodium 2-thioethanesulfonate hydrate with 50% probability displacement ellipsoids. H atoms are omitted for clarity. The complete coordination of the Na atom is shown. Symmetry codes: (a) x, -1+y, z; (b) x, 1+y, z; (c) 1/2-x, -1/2+y, -1/2+z; (d) 1/2-x, -1/2+y, 1/2+z; (e) 1/2-x, 1/2+y, -1/2+z; (f) 1/2-x, 1/2+y, 1/2+z.