I cant help you but one of the local operators does beach landings on masons bay, stewart island and they always carry the shovel and some planks of wood just in case. Its a matter of dig the exit, place the boards and unleash the almighty lycoming horses, leave the boards behind - they are still growing trees! Judging by how easy it is to get stuck on a beach in a car I think its worth while checking a beach condition before going there, the sand surface can be very deceiving!