The synthesis of an endohedral C60 fullerene containing a single trapped H2O molecule was recently achieved [K. Kurotobi and Y. Murata, Science 333 (2011) 613-616]. In this Letter, a computational study is conducted to determine the dynamic properties of the trapped water for a range of temperatures between 50 and 300 K. MD and ab initio MD (AIMD) simulations show that, in the absence of hydrogen bonds, the orientational relaxation of H2O inside the fullerene cage is fast and nearly temperature independent. These properties could be exploited in the design of future nanotechnologies. (C) 2012 Elsevier B.V. All rights reserved.