Interaction of water with ionizing radiation is, in addition to direct DNA damage, causing radiation damage in living organisms and it is also important for nuclear waste treatment. Upon photoionization in water an electron and a cationic hole are formed, therefore, we follow the fate of both. To the former, we present a computational study of the structure and dynamics of an excess electron in a medium-sized water cluster aimed at addressing the question of interior vs. exterior solvation, electron localization and its quenching with a hydrated proton leading to the formation of a hydrogen atom. To the later, we calculate the ultrafast relaxation of a cationic hole in water dimer and in the aqueous bulk followed by formation of an OH radical. Ab initio Born-Oppenheimer molecular dynamics simulations are performed within the density functional theory framework, employing a hybrid Gaussian and plane waves formalism together with the PBE or BLYP exchange-correlation functionals corrected for the self-interaction error and augmented by an empirical dispersion term.