Make sure the burlap has been soaked before you leave the vendor, Line the bottom of your cooler with ice maybe 6". Place a couple or more layers of heavy cardboard on top of the ice and spread the oysters out in the sack and lay them on the cardboard. Put mor cardboard on top and thin layer of ice.
i hauled 44,000 lbs from Kemah to Va. Beach in reefer and maintained 44 deg. What I described is the closest I can come to that environment.
IN OTHERWORDS KEEP THEM COOL AND MOIST AND THEY WILL LIVE