The title compound, C(11)H(10)N(2)O(4)·H(2)O, has a zwitterionic structure, in which the benzimidazole ring system is planar, with a maximum deviation of 0.007 (3) Å. The carbox-yl/carboxyl-ate groups adopt a trans configuration. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds involving the hydr-oxy/oxide O atoms link the mol-ecules into a one-dimensional chain. These chains are further linked by O-H⋯O hydrogen bonds involving the water mol-ecules into a two-dimensional network. π-π contacts between the benzimidazole rings [centroid-centroid distance = 3.5716 (4) Å] lead to the formation of a three-dimensional supra-molecular structure.