This is a very old toy. You fill a small container in the tin boat with water and light a small candle underneath. The water heats up quickly and the escaping steam makes the boat go, making a nice pop..pop… sound. Nice toy for the bathtub, which is a lot of fun for children and also explains a bit of physics. However, according to current regulations, like most tin toys, it is not approved as a toy. So it’s better to try it out in the company of adults.