The mole plough allows under-drainage to be installed without trenches, or breaks up the deep impermeable soil layers that impede it. It is a deep plough with a torpedo or wedge-shaped tip and a narrow blade connecting it to the body. When dragged over ground, it leaves a channel deep under it that acts as a drain. Modern mole ploughs may also bury a flexible perforated plastic drain pipe as they go, making a more permanent drain – or may be used to lay pipes for water supply or other purposes. Similar machines, so-called pipe-and-cable-laying ploughs, are even used under the sea for laying cables or for preparing the earth for side-scan sonar in a process used in oil exploration.