Classic Pop Pop / Steam Jet Boat / Candle Boat with Jet Propulsion. "The pop-pop, putt-putt, or puff-paff boat is a toy boat with water impulse propulsion (steam jet propulsion, pulse motor, pulsed waterjet). The simple engine operates without moving parts such as pistons, valves, or wheels. A candle or another heat source serves as the energy source. At the stern of the boat, two pipes protrude side by side and parallel below the waterline. Water is drawn in and expelled through the pipes. The characteristic rattling noise that gives the boat its name is not directly caused by the evaporation process but by a special construction of the evaporator: The top is made of spring steel sheet shaped like a clicker frog, which jumps back and forth during the rapid pressure changes, producing a clicking sound each time." (Source: Wikipedia) The boat then travels on an unpredictable route. Material: Tin Size: approx. 14 x 6 x 2.5 cm (L x W x H)