Water and water-dimer encapsulations into D5h-C70 and D2(22)-C84 & D2d(23)-C84 fullerenes are evaluated. The water-dimer equilibrium populations are computed using the potential-energy change from the ab initio G3 theory and anharmonic partition functions from the MP2/AUG-cc-pVQZ approach. The encapsulation energetics is treated at the M06-2X/6-31++G** level and it is found, for example, that the water-dimer storage in C84 is attractive, yielding an energy gain of more than 10kcal/mol. This substantial encapsulation energy together with the computed temperature increase of the water-dimer population in the saturated steam suggest that the (H2O)2@Cn endohedrals could also be produced in a
high-temperature/high-pressure approach similarly to encapsulation of rare gases in fullerenes.