Added you as a friend because of your guide on SH3, but you seem gone.
Compare this guide that I found on the net:
www.donitzeliteflotilla.com/forum/index.php?topic=54

Even just in training, I have a hard time with sinking the ships. Some I end up disabling but they won't go down. Others that should be hits, it's like the torpedo goes right through their ship as a phantom torpedo.

Added you as a friend because of your guide on SH3. The book never explains the color of the arrows when torpedoing. You have red, orange, yellow, and green.