Well, I have NO idea if it works in GWX2. I have yet to get in a position to test it out.

However, in the earlier releases of GWX, it was quite possible. I forget if it worked better with impact or magnetic detonators, but it worked. The only problem is that the ship is sunk via flooding, so you have to wait a long time for it to sink.

I've also noticed (again, I haven't tested this in GWX2, yet) that in the earlier relases, the same was true with the bow of the ship. A single shot to the bow of most ships would also doom them, with only the largest of ships possibly needing another torpedo.