Actually, it's the compass you are already using!
You're probably close enough tom drive up PA take underwater nav with Jim, but if stay close home any underwater nav course will be adequate. As Jim said you should get into habit using compass every time you dive.
The luber line is just to keep you oriented. If you are boat diving for example, take a reading in the direction you are starting, and 180 will lead you back t where the boat is. For example, if you head away from the boat at 240, then assuming went relatively straight direction you head back at 60.
Don't forget keep heading in the window, and kee compass level. If you don't want swim with your eyes on compass every second pick a spot in front of you and swim to that spot.
For example, heading back keep compass point in window in direction you are going, say 180. Look ahead and see what landmark is in front of your compass. If its a kelp, rock, coral, etc the you don't have to keep eyes on compass, just swim to landmark. Once get there, repeat compass heading, pick landmark in front, keep going. Repeat until arrive destination.
One of the best drills however for underwater navigation is doing square and triangle patterns underwater. Practice a few times and the compass becomes essential dive gear, not just some crazy contraption comes in console.
After my underwater nav class for AOW my confidence in underwater navigation has grown exponentially. Thanks to a great instructor I'm now the diver others look to when it's time head back. My last dive with dive club we were sitting in the sand looking at our compasses. Some of the diver's pointed in one direction, and I knew it was the wrong way. I had previously set my lubber line to home and pointed back the other way to go home. I was right.
As Jim says, this only happens if you get into the habit using compass each and every dive. There really isn't anything wrong with your compass, you just have to become more familiar with how to use it.
Fun and safe diving.