That is some picture of damage!!!!!!!!!!!!!!!!

Just goes to show you that water tight doors and bulkheads will keep a ship afloat. With that said and the picture present, the SH3 merchants are modelled as it they have bulkheads and sections. So if you keep sending in torpedos to the same spot, it is more or less a waste as that section is already flooding. Each torpedo should hit different sections of the ship thus in theory opening up the ship to sea more!