Exohedral reactivity of endohedral fullerenes has aroused a significant interest because of its potential applications. The present letter examines the effect of an entrapped single water molecule on the reactivity of C-60. We study the thermodynamics and kinetics of a Diels-Alder reaction occurring at all nonidentical bonds of free C-60 and H2O@C-60. Our calculations show that encapsulation of water does not have a significant effect on H2O@C-60 reactivity compared to C-60, as attested by the investigation of the reaction under several orientations of H2O inside C-60. Reaction and activation energies indicate that [6,6] bonds are the most reactive sites. (C) 2017 Elsevier B.V. All rights reserved.