The results of a theoretical study of the I-H2O anion and its neutral precursors are presented. The hydrogen-bonded structures were predicted for both the ionic and neutral complexes. The energetically preferred isomer for IH2O however is a species with the direct O-I bond. The relation between the potential energy surfaces for ionic and neutral moieties is evaluated based on their electron affinity properties. Thermodynamic and spectroscopic (IR) properties of complexes are discussed. The interaction energy decomposition is applied to explore the differences between the nature of bonding within the studied complexes.