The sound of the harpoons lodging themselves into the cabin door could not be missed from within said cabin. Figuring the door would not hold out for long, Joseph brought it into his field of vision and kept it there, preparing to use his septima to toss one of his already packed large aluminum suitcases at whoever tries to get through it. With it's weight it should be enough to both knock over a human and leave a mark, likely even broken bones, depending on how it makes contact. Most armor would be useless against such a blunt force, especially armor that retains most mobility. The suitcase would likely be scratched and dented, but it should be strong enough to survive the impact without opening up.
Mr. Leidner wondered how the intruders would react to a suitcase flying towards them at speed.

If there were too many for this one hurl to take care of them, he could always pull the thrown case back to himself with the same ability, but he also had the other suitcase he was almost done packing.

As the door was forced open, and the first diver started entering, Joseph tossed his luggage shouting: "Don't interrupt me while packing!", as his gravity slingshot accelerated the packed suitcase into the diver at the rough velocity of a non-professional's baseball pitch.