Ocean liners are a travel topic.

Before the widespread adoption of air travel, trans-oceanic crossings by necessity relied on ships which plied the high seas. While the first crossings were made by sailing vessels, steamships became common in the mid-19th century; by the early 20th century, ocean liners of various rival lines competed aggressively on both speed and luxury.

Unlike cruise ships (which are built as floating hotels for entertainment), ocean liners were constructed as practical transportation and built for speed, for longer routes than ferries. Thus they usually had a higher passenger capacity than a cruise ship of similar size and with very few exceptions also carried cargo and/or mail.

History

From Magellen's initial circumnavigation of the globe (1519-1521) to the mid-1800s, seafaring was powered by the winds and was a slow, arduous and sometimes risky means of travel. A trans-Atlantic crossing routinely took two months; arrival times were unpredictable and very much at the mercy of the wind and waves. The 1837 entry of the steamship SS Great Western in trans-Atlantic service cut this to 15 days. Cunard Line’s RMS Britannia provided scheduled passenger and cargo service from Liverpool to Boston in 1840; by 1847 iron-hulled vessels with propellers displaced paddlewheelers, improving the vessel's efficiency. White Star Line’s RMS Oceanic (1870) offered large portholes, electricity and running water in its first-class cabins; from 1880 ocean-growing liners increased in size to meet the needs of a growing number of immigrants. In 1872, Jules Verne predicted a trip Around the World in Eighty Days by steam to be within reach of passengers on that era's commercial vessels, with the overland portions completed mostly by rail; a pair of rival US journalists each completed a world tour in under eighty days in 1889. Marconi's wireless telegraph began to appear shipboard after the turn of the century.

In the early 20th century, rival lines competed aggressively on both luxury and speed of travel. The Blue Riband, an honour conferred on the passenger liner in regular service capable of making the fastest average speed on a westward North Atlantic crossing, was hotly contested. The designation "Royal Mail Ship" was highly valued by shipping lines; if a contract for postal mail delivery paid well but imposed onerous per-minute penalties for late arrival, the mail ship was presumed punctual and operated by necessity to a tight schedule.

In a few high-profile incidents, liners met with deadly misfortune at sea; the RMS Titanic sank in 1912 with 1514 souls lost after a collision with an iceberg, the RMS Empress of Ireland sank in 1914 with 1012 souls lost after collision with another ship, the civilian passenger liner RMS Lusitania was torpedoed and sunk in 1915 by an enemy U-boat attack with 1,198 dead during the Great War, World War I. Many liners were converted to military service during the Great War, where (with aviation still in its infancy) they were essential to the war effort. By 1917, the conflict had descended to the level of unrestricted submarine warfare, with substantial losses to both civilian and military shipping.

The Great Depression were hard years for the passenger lines as few could afford to travel and fewer still could afford to travel in luxury. The post-World War 2 era brought further decline, as falling prices of air travel as well as technological advances brought trans-Atlantic jet flights within the reach of much of the middle class. Ocean liners still exist and still ply the seas, but they are a dying breed.

Vessels in active service

• RMS Queen Mary 2, a trans-Atlantic passenger liner of the once-famous Cunard line, has operated seasonally between Southampton and New York City since 2004.
• MV Claymore II, a passenger/cargo liner, provides an essential transport link to Pitcairn Island from New Zealand and French Polynesia.
• RMS St Helena, a passenger/cargo combiliner, serves the British overseas territory of Saint Helena from Cape Town, continuing to Ascension Island.

Liners operating as cruise ships

• MS Marco Polo operates as a cruise ship under charter to UK-based Cruise & Maritime Voyages.

Floating hotels

A few former ocean liners are now in use as hotels or museum ships at one fixed location:

• RMS Queen Mary, Long Beach, California, USA. Originally one of a pair of Cunard liners in scheduled transatlantic service (alongside the original Queen Elizabeth), the original Queen Mary was retired in 1967 and permanently moored as a museum ship with restaurants and a hotel. Queen Elizabeth 2, operated by Cunard as both a transatlantic ocean liner and a cruise ship from 1969 to 2008, is currently in Dubai; as of 2015, a proposed deployment as a "floating hotel" has yet to materialise. 

• SS Rotterdam, Rotterdam, Netherlands. The fifth SS Rotterdam served as an ocean liner and cruise ship from 1959-2000; the last great Dutch "ship of state", the Grande Dame has operated as a hotel ship in its namesake city since 2010. 

• MV Veronica, Duqm, Oman. Built as MV Kungsholm in 1966 as a combined ocean liner/cruise ship for the Swedish American Line and later rebuilt as a full-time cruise ship, this ship operated under various names (MV Sea Princess, MV Victoria, MV Oceanic II and MV Mona Lisa) before being retired in September 2010. The Korean Daewoo company moved the ship to Oman as the Veronica floating hotel. 

Museum ships

• Hikawa Maru (氷川丸?), Yamashita Park, Naka-ku, Yokohama, Japan. One of a matching group of three liners which plied a route between Yokohama, Vancouver and Seattle for Nippon Yūsen Kabushiki Kaisha ("NYK Line") from 1930 onward. Now permanently docked as a museum ship, its sister ships were both lost in the Second World War. 

• SS United States, a luxury passenger liner built in 1952 for United States Lines, operated in transatlantic passenger service until 1969. Docked since 1996 at Pier 82 on the Delaware River in Philadelphia, this vessel was once the fastest liner on the trans-Atlantic crossing and is being preserved for future use as a museum ship.

Royal mail ships

See also: Postal service#Postal history

While British Airways, as flag carrier of the United Kingdom, is the de-facto carrier of record for the now-privatised British Royal Mail company, a handful of ships retain some form of the Royal Mail designation for historic reasons.

The four ships in the world still carrying the status of Royal Mail Ship or Royal Mail Vessel are:

• RMS St Helena, which serves the British overseas territory of Saint Helena, carries Royal Mail as (due to a lack of facilities) St. Helena is not accessible by aeroplane.
• RMV Scillonian III serves the Isles of Scilly, where access is otherwise somewhat limited.
• RMS Queen Mary 2 of the Cunard line retains the status as an acknowledgement of the historical service of her predecessors as Royal Mail Ships.
• RMS Segwun, a restored 1887-era steam-powered passenger vessel in Gravenhurst, Ontario, is recognised as a Royal Mail Ship by Canada Post as it occupied the role historically.

Museums and memorials ashore

Between 1912-1915, more than 3,700 perished at sea during the loss of RMS Titanic (which struck an iceberg), Empress of Ireland (which collided with another ship) and RMS Lusitania (torpedoed by a German U-boat in the Great War).

• Kinsale Museum, Market Square, Kinsale, Ireland, ☏ +353 21 4777930. Local military museum covering the Battle of Kinsale and the 7 May 1915 U-boat attack which sank Cunard's RMS Lusitania off the Old Head of Kinsale, killing 1,195 of her 1,959 passengers. Lusitania was returning to Liverpool from New York City; her loss was a factor in the US decision to enter the Great War (World War 1). 

• Lusitania memorial and gravesites in Cobh (near Cork, Ireland): there's also a memorial at Old Head of Kinsale (whose lighthouse is 11 miles from the shipwreck) and a gravesite at St. Multose Church in Kinsale.

• Merseyside Maritime Museum, Albert Dock, Liverpool L3 4AQ, United Kingdom (on waterfront), ☏ +44 151 478-4499. 10am-5pm daily. Museum with permanent gallery devoted to the Titanic, Lusitania and Forgotten Empress. free. 

• Cité de la Mer, Gare Maritime Transatlantique, 50100 Cherbourg, France. Marine museum in 1933 art-deco Transatlantic Terminal building. The museum describes the lives and history of emigrants departed by sea from France to the New World; a 2012 exhibit recalled the 100th anniversary of the RMS Titanic. 

• Empress of Ireland Museum, 1000, rue du Phare, Rimouski G5M 1L8, Canada, ☏ +1 418-724-6214, fax: +1 418-721-0815. One museum within "Site historique maritime de la Pointe-au-Père" describes a May 29th, 1914 collision in fog between the Canadian Pacific steamship Empress of Ireland and Norwegian coal steamer Storstad which killed 1,012 of the "forgotten Empress'" 1,477 passengers and crew. $9/person (museum), or $14.75/person to tour the museum, lighthouse and the RMCS Onondaga (1967-2000) submarine.. 

• Maritime Museum of the Atlantic, 1675 Lower Water St, Halifax B3J 1S3, Canada, ☏ +1 902-424-7490. 9:30am-5pm. Marine museum with extensive permanent exhibits of RMS Titanic artefacts and history of the Great War explosion of a munitions ship in Halifax harbour. C$8.75/person. 

• The Titanic cities tour includes various museums and memorials to ship, crew and passengers, from the shipyards of Belfast and the vessel's primary point of departure in Southampton to the graveyards of Halifax which became the final resting place of hundreds of Titanic voyagers. Many of 1,517 lost (of the 2,228 people on board) were buried at sea. The last of the survivors was buried at sea at pier 44, Titanic's original departure point in Southampton, in 2009.

See also

• Cruise ships
• Freighter travel — no guaranteed berths, and even no guaranteed departures, but this is sometimes the only way to plough the waves