In the Feynman Lectures, Richard Feynman makes the following statement:
The particular crystal pattern of ice shown here has many “holes” in it, as does the true ice structure. When the organization breaks down, these holes can be occupied by molecules. Most simple substances, with the exception of water and type metal, expand upon melting, because the atoms are closely packed in the solid crystal and upon melting need more room to jiggle around, but an open structure collapses, as in the case of water.
It explains ice melting, but what does he refer to by saying "[...] these holes can be occupied by molecules. [...]"? Does it mean that when ice melts, the water molecules fill the empty spaces left by the atoms?
I am not sure if my question is properly formatted, if you need more information I can edit it. I would appreciate if someone explains this particular topic a bit deeper.