They call it live rock, but trust me, that stuff is most likely drop shipped. Rock is shipped from Indo or Africa, or wherever, in large containers. It takes days, and sometimes weeks before it gets to your LFS
. It is not submerged in water, it's merely wrapped in some damp newspaper.
What is the difference between this and dry rock? There is dead stuff on this rock. If the difference is dead stuff, then why is it called "live" rock in the first place?
How they ship it to you is of no consequence. The small amount of creatures that make it to your aquarium were against all odds. The ratio of living creatures making it V.S. the ones that didn't, is amazing. Some times there's nothing living on the rock but spores.
The same goes for live sand. It's just a way to market the sand. There is nothing live on that sand when you pull it off the shelf and put it in your tank. It's not like the sand is aerated and heated in water until you get it.