In the title compound, C(12)H(14)O(4)·H(2)O, the dihydro-benzo-furan ring adopts an envelope conformation with the substituted C atom 0.142 (1) Å out of the least-squares plane. In the crystal, the components are linked via inter-molecular O(water)-H⋯O and O-H⋯O(water) hydrogen-bonding inter-actions, forming a three-dimensional network.