well, "live" rock is nothing more than rock with bacteria on it. all the hitch hikers that may or may not come with it are bonuses, or curses, depending on the hitch hiker.
we use rock from the ocean because we are sure it's safe to use, and is what the natural marine habitat is made out of.
actually, it's probably better to use man-made rock or base rock that you are sure is void of life, just so that you can start your ecosystem from scratch. then you are sure you won't get a single bad hitch hiker.
, leaving rock in 40 degree water for an extended period is almost the same as drying it out. a good portion of the critters won't survive.