It is a vessel that transfers a large quantity of liquid cargo such as petroleum products, diesel, syrup, glucose, undiluted wine, chemicals not in a container and simply called a tanker. Liquid cargo, in general, changes its volume according to temperature changes and due to there remains risk of a fire as well as dynamic stability performance of a vessel according to the status of liquid cargo, it has a special structure.

The size is classified into Mammoth Tanker, Super Tanker, VLLC and ULCC by size ranging from several thousand tons to tens of thousand tons.