Water freezes to ice by cooling. Once ice is formed, the phase does not change unless heated over the melting point. This is a familiar phenomenon observed in our everyday life. Here, we demonstrate non-bulk-like behavior of nanosized ice by molecular-dynamics simulation using the TIP4P potential. Our 100 micros simulations reveal that the structure of the (H(2)O)(20) nanocluster reversibly changes and a variety of solidlike phases, such as bilayer structures composed of three pentagonal prisms, square and pentagonal ice nanotubes, and stuffed-fullerenelike (H(2)O)@(H(2)O)(19) structures, dynamically coexists even at 52% of the bulk melting point.