There are two schools of thought, and the jury is still out as to which is better: lots of water or barely enough water to keep the nem wet. Obviously, it would be cheaper to ship a nem with just a little water.
Talk to your LFS and see which they recommend -- it would probably be based on what they see come in from their wholesaler/exporter and the morality rate.
That said, what kind of nem are you trying to ship? Some will handle shipping better than others.