Water under extreme pressure turns into ice, but some different kind of ice.

In the new experiment. . . the volume of "water shrank abruptly and discontinuously, consistent with the formation of almost every known form of ice except the ordinary kind," according to a Sandia statement Thursday.

Apparently, there are at least 11 other types of ice that most of us don't know about. They're classified by how they behave at certain temperatures and pressures.