In the title compound, C19H21N3O5S.H2O, the central indazole system is essentially planar (r.m.s. deviation = 0.012 angstrom), while both the benzene ring and the mean plane defined by the nonH atoms of the ethyl propionic ester unit (r.m.s. deviation = 0.087 angstrom ) are nearly perpendicular to the indazole plane, as indicated by the dihedral angles of 82.45 (8) and 75.62 (8)(degrees), respectively. Consequently, the molecule adopts a U-shaped geometry. In the crystal, the water molecule, which is linked to the indazole system by a strong O-H center dot center dot center dot N hydrogen bond, is also involved in two additional N-H center dot center dot center dot O and O-H center dot center dot center dot O interactions, which link the organic molecules into chains along the b-axis direction.