Rescue from quicksand near Mont St. Michel

From notes re the Bayeux tapestry:

"Harold accompanies William and the Norman soldiers as they set off to fight Duke Conan of Brittany. They pass Mont St. Michel, which is on the border between Normandy and Brittany. To get into Brittany they have to cross the river. They hold their shields above their heads to keep them out of the water. Some soldiers sink into quicksand and Harold rescues them - two at a time!"

On a more prosaic note, does anyone know whether there are roads on the island itself, beyond the causeway.  It looks too crowded with structures to accommodate roads, so I'm wondering how a resident would have large items delivered...

Photo credit.