In the last scenario of Operation Cyclone: "Das Boot", which weapons exactly can sink the submarine? It is Armor 6, Health 3, and from what I understand the damage you inflict is not cumulative, so in order to sink it, you must inflict at least 3 damage with a single weapon in a single attack.
So anti-tank weapons that are unable to cause it any damage include: Mickey's howitzer, Honey's phaser, the Laser Werfer and Luther's Flak.
Demo Charges and Panzerfausts can damage it, but are unable to inflict more than 2 hits in a single attack.
The dangerous weapons which can pierce the sub's hull are: Panzerschreck, Ludwig's cannons, Kampfzange, Hermann's laser, Bazookas and the Pounder.
My biggest doubt is concerning flamethrowers and napalm throwers. Theoretically they can damage Armor 6 units, but the rules say that their flame nature prevents them from damaging structures like tank traps. So is a flame weapon able to pierce a submarine's hull?