As you gave sharpies as option, you seem to want see the drawing when finished with the water colour.
In that case, use whatever waterproof marker you happy to draw with, as the lines will be well visible, you need to draw in such a way that the lines are as you want them to be in the end result.
Pencil lines will work as well, if less obvious, as long as ...
Because watercolor layers are transparent and thin, any hard pencil marks will most likely be visible through the paint at the end.
THE "NICE" WAY
I recommend using your pencil lightly when you are creating your initial sketch/map and erase at least partially afterward, if possible.
I also recommend you using a 9H pencil or some "H" ...