The cyclic water-trimer encapsulations into D-2(22)-C-84 fullerene are evaluated. The encapsulation energy is computed at the M06-2X/6-31++ G** level and it is found that the trimer storage in C-84 yields the potential-energy gain of 10.4 kcal/mol. The encapsulated trimer can have two different forms, either the conformation known with the free gas-phase water trimer or the arrangement with the three nonhydrogen bonded H atoms on the same side of the O-O-O plane. The latter endohedral isomer is lower in the potential energy by 0.071 kcal/mol and forms about 57% of their equilibrium mixture at room temperature. (C) 2018 Elsevier B. V. All rights reserved.