Sure it becomes much simpler if you remove the diving aspect to it, or simply remove the need to return to the surface alive.
I would suspect dragging an explosive with a rope would take a long time, enough that radar and other ships would likely notice the behavior, especially if you intend to hit the pipeline 3 times on 3 different locations. Really expensive sonar would reduce the required time, as would really precise GPS locations, but even so, from what I know, it a very time consuming activity. Still a better theory than sport diving.
