It is LIVE because it houses the beneficial bacteria that convert ammonia to nitrite and nitrite to nitrate. Deep within the rock are anoxic areas that house the bacteria that eat nitrates and turn them back inot nitrogen, which is where the cycle starts and ends.
from the sea may also contain a myriad of creatures that will sprout over time. Amphipods, copepods,isopods, bristle worms, feather dusters, anemones, etc. Some may also have corals, a/o sponges on them. You may also end up with a pistol or mantis shrimp, variuos types of crabs, etc.