This is a simple system of 260 water molecules.

In this example, the coordinates of the atoms are read from a PDB file
instead of being specified manually (as well as the boundary information).

The PDB file was generated by the useful "solvate" utility which comes with VMD.
(To generate this file yourself, run VMD, click on the "Extensions" menu, 
and select Modeling-->Add Solvation Box.
In this example, I made a box whose x,y,z dimensions were 16,24,24.)

