A boat propeller is a device used to propel a boat through the water. It can be powered by oars (OAR), a pole (POLER), a punt (PUNTER), a SCREW (SCREW) or STEAM (STEAM). Oars are the simplest form of propulsion, using a person's strength to move the boat. A poler is a long pole used to push a boat along in shallow water. A PUNTER is a flat-bottomed boat that is propelled by a pole. A SCREW propeller is a device with blades that spin to create thrust and move the boat forward. Finally, a STEAM propeller is powered by a STEAM engine and is the most powerful type of boat propulsion.