The guys at ORW turned me on to commercial restaurant kitchen floor mats for sandy desert off road excursions in Anza Borrego. Cut it in two and slip it under the tires if you get stuck. Its some kind of rubber material so it won't rust around salt water.
Last time I was out, some tourist drove his car on the beach and parked right in the middle of the entrance and left it there. The lifeguards took care of it.
