Not a bother mate, I know where you are coming from lol. A few years ago I would probably have agreed but to my way of thinking now, anything that will help is a bonus.
I have been told about loads of marks but when I have actually got to them and am stood there waiting to cast out I usually find myself thinking am I right here. If you keep trying different spots around the mark you will probably find it eventually. The point we were making about the compass is, when you manage to find the gulley or hole you are looking for then you can take a note of exactly where you are casting and remember it for a future date.
As you said before when you have the experience, gained over the years you can use it but Tony has just come back to fishing and is trying to find out more about it.
As I said earlier, anything that will help to locate a good mark to fish from is a bonus at the moment. Personally I would try just about anything lol.
Jim.