I had to do this not very long ago and it was a really pain. I've had my liverock for a long time, and it's covered in polyps, mushrooms, etc, so I put it all in a 35 gallon rubbermaid tub and filled it with tank water. The rock made it just fine. I packed the tub (with lid on, obviously) in my car and piled a bunch of blankets around it to keep it warm. I think just about everything on the rock made it. The fish and corals I packed up into bags with tank water and oxygen and put them in styrofoam coolers. All the fish and most of the snails, starfish, hermit crabs etc. made it, but some of the corals and clams did not. I think they may have gotten too cold, my SPS corals took the biggest hit. I'm pretty sure the heaters I used were not strong enough, or maybe didn't last long enough. It was probably 30 hours from bagging up to acclimating back into the tank. I did take them into the hotel when I stopped for the night, but for whatever reason, I didn't pack them well enough Anyway, if you pack them up well, and drive like heck, you should do OK. If you've ever ordered from on online store follow their lead (SWF has always done a good job for me -shameless plug, I know!) HTH