Types of sea transportation include ships, hydrofoils, boats, submarines and boat-cars. Ships range from ferries and cruise ships to steamships, cargo ships and naval ships. Boats are smaller than ships, and include speedboats, sailboats and houseboats.
Sea transportation is slow compared to most versions of land or air transport, but it is less expensive than those modes of transportation and is useful for transporting non-perishable goods in large quantities. As of 2007, 7.4 billion tons of these goods were transported by sea worldwide, much of them on container ships. Standardization of cargo containers was a driving force behind the growth of the shipping industry beginning in the 1950s.
Naval ships are used to defend countries in peacetime and war alike and range in size from small service craft to enormous aircraft carriers. Submarines, which are able to travel under the water, are primarily used in national navies, though some are also used for scientific exploration.
Sea transportation can also be practical on a smaller scale, as with ferries that transport cars and people short distances. Many people take to the sea for recreation as well, either on large ships such as cruise ships or on smaller boats that allow them to go fishing, sightseeing or just to relax.