There are three main ways in which goods are transported on ships. These affect how different ships are built. For more information, see the page in this guide on the different types of ocean shipping.
Goods shipped in containers
The use of containers dominates commercial international shipping. The advantages of packing goods into containers include:
the ease of intermodal transit, ie containers can be unloaded from the ship and transferred directly to a road or rail vehicle
the opportunity to offer consumers a door-to-door service
speed and efficiency of loading and unloading
security of goods during transit
There are more than 20 internationally recognised types of container, including refrigerated units and open-topped containers, but there are two basic sizes. Their dimensions in metric terms are:
20ft: 589cm (l) x 235cm (w) x 239cm (h) - volume 33.2 cubic metres
40ft: 1,203cm (l) x 235cm (w) x 239cm (h) - volume 67.7 cubic metres
The largest container ships can accommodate more than 9,000 20ft containers.
Goods shipped as break-bulk
Break-bulk refers to any non-bulk cargo that isn't containerised (such as goods on pallets, or in crates or drums or sacks), which is loaded directly into a ship's hold. Break-bulk tends to be used for specialised trades (such as fresh fruit), or for trade to small ports that do not have the necessary infrastructure to handle containerised traffic.
Goods carried as break-bulk can be more susceptible to damage than containerised goods because they are stowed loose in a ship's hold. So strong packaging is essential, as is dunnage (loose packing material), which is placed around the cargo to protect it from damage during transit - see how to label and package goods being shipped out of the UK.
Goods shipped in bulk
Large shipments of certain commodities - such as coal, ore, wheat or oil - are typically carried in bulk, unpackaged in the ship's hold.