On most all general cargo ships, and on any number of other ships, going forward from the engineroom to the end of number two hold will be a pipe tunnel. In the pipe tunnel you will find steam pipes going to fuel oil tanks. Most ships use bunker oil for fuel. Bunker oil is almost as thick as tar and needs steam to heat it in order for it to be able to be pumped. Some will burn the fuel directly in the engines, while others will burn it in large boilers, and the steam created runs the engines, these are called steamships.