I have looked on the internet about tubular fossils, and I don't think that is one. If it comes from the sea, that probably made that mark. The salty waters will probably make all rocks become miscolored on the surfaces over time. Also it could have collided with another rock when in rough waves and made it.
I take it these are on opposite sides of the same rock...
These have a similarity to a limpet mark, but the mark in the middle needs to be explained too.
It is fundamental to know whether these are just surface markings or whether they go right through the rock.
Is it possible you could saw the rock in half to test that?
If so, I suggest you do it carefully so you don't damage the existing marks. You do this entirely at your own risk, but I might suggest using an angle grinder with a stone-grinding blade or a diamond cutting blade. Make sure the rock is firmly clamped (not easy). You could saw just part-way through, then split it with a hammer and chisel (again, take precautions).
If you manage it, and the mark does go right through, my mind is going towards fulgurite - the result of a lightning strike. But even with that, there are several things that are not right. Also, fulgurites are very rarely found.
If the primary mark/object is in the middle, the halo needs to be explained. It is the sort of thing that occurs in concretionary processes, but even there, it does not feel right.
If the mark is surface-only, another possibility is a seaweed holdfast mark.
Anybody else got some ideas?
If not, I think this might be one to bring/send to the Angela Marmont Centre for closer inspection!