The electronic spectra of Co+(H2O), Co+(HOD) and Co+(D2O) have been measured from 13500 cm-1 to 18400 cm-1 using photodissociation spectroscopy. Transitions to four excited electronic states with vibrational and partially resolved rotational structure are observed. Each electronic transition has an extended progression in the metal-ligand stretch, v3, and the absolute vibrational quantum numbering is assigned by comparing isotopic shifts between Co+(H216O) and Co+(H218O). For the low-lying excited electronic states, the first observed transition is to v3'=1. This allows the Co+-(H2O) binding energy to be determined as D0(0 K) (Co+-H2O)=13730±90 cm-1 (164.2±1.1 kJ/mol). The photodissociation spectrum shows well-resolved Ka band structure due to rotation about the Co-O axis. This permits determination of the spin rotation constants ϵ_aa^''=-6 cm-1 and ϵ_aa^'=4 cm-1. However, the Ka rotational structure depends on v3'. These perturbations in the spectrum make the rotational constants unreliable. From the nuclear spin statistics of the rotational structure, the ground state is assigned as 3B1. The electronic transitions observed are from the Co+(H2O) ground state, which correlates to the cobalt ion's 3F, 3d8 ground state, to excited states which correlate to the 3F, 3d74s and 3P, 3d8 excited states of Co+. These excited states of Co+ interact less strongly with water than the ground state. As a result, the excited states are less tightly bound and have longer metal-ligand bond lengths. Calculations at the CCSD(T)/aug-cc-pVTZ level also predict that binding to Co+ increases the H-O-H angle in water from 104.1° to 106.8°, as the metal removes electron density from the oxygen lone pairs. The O-H stretching frequencies of the ground electronic state of Co+(H2O) and Co+(HOD) have been measured by combining IR excitation with visible photodissociation in a double resonance experiment. In Co+(H2O) the O-H symmetric stretch is ν1"=3609.7 ± 1 cm-1. The antisymmetric stretch is ν5"=3679.5 ± 2 cm-1. These values are 47 and 76 cm-1, respectively lower than those in bare H2O. In Co+(HOD) the O-H stretch is observed at 3650 cm-1, a red shift of 57 cm-1 relative to bare HOD.