Passive torpedo is a good idea, but be sure to set the speed to 40 knots. 55 and it won't work.
Another old trick from 688i that works is to make sure your torpedo depth is just under the surface and just above the floor, so the torpedo can search a larger area.
If you're in very deep water to the floor, just set it real deep somewhere.
Last but not least, don't forget about snapshots. Especially against a better sub, they can come in handy.
And drop the movie tactics.
