They had no weapons.
The weapon described is a depth charge.
Submarines and Aircraft Carriers
No,but you can hold a secondary weapon in your hand and a primary weapon on your back,or a primary weapon in your hand and a secondary in your holster.
Allied cargo ships were the Germans primary targets.
Oilers then merchantmen.
Submarines are not barbaric weapons. However, some tactics, such as unwarned attacks were considered by some during WWII as barbaric. As with most things, the thing is not bad, but how it is applied can be.
Torpedoes were the main weapon. The submarines also had a naval gun that they would use on unarmed ships and many had machine gun mounts as well.
a ninjato or a shrukien
whip
they used U-boats, which are German submarines.
No - all submarines, be it nuclear or diesel-electric, use diesel fuel, either for primary engines (DE) or backup generator (nuclear).