The potential energy surface of the (H2O)(5) water cluster is examined using Kohn-Sham density functional theory, Hartree-Fock theory and second-order Moller-Plesset theory. Two distinct minima on the energy surface maybe interconverted through the transfer of two hydrogen atoms, representing a possible mechanism for ionic dissociation in water clusters. Our calculations suggest a concerted mechanism where the two hydrogen atoms move simultaneously through a late transition state.