I have a huge boulder in my front yard that is in no way moving (it's 4 feet tall or so, by a similar length). It will make an awesome center piece for a water feature (perhaps the beginning of a pond-less fall/stream). The question goes as follows, if I do run water down it how do I make sure that there will be no leaks where the liner meets the boulder? Is there an adhesive that will work well enough? I am also considering digging under it and setting the liner under it just enough and then encourage flow away from the boulder? In simple terms, if you can't lift a boulder and put a liner under it, how do you make a water feature out of it? I figured I would ask the professionals before attempting anything. I just bought the house and have yet to dig around and see how it sits. I will also get some pictures as time allows. Thanks in advance!