MS Estonia, previously Viking Sally (1980–1990), Silja Star (1990–1991), and Wasa King (1991–1993), was a cruise ferry built in 1979/80 at the German shipyard Meyer Werft in Papenburg. The ship sank in 1994 in the Baltic Sea in one of the worst maritime disasters of the 20th century. It is the second-deadliest European shipwreck disaster to have occurred in peacetime and the deadliest peacetime shipwreck to have occurred in European waters, with 852 lives lost.
The Estonia disaster occurred on Wednesday, 28 September 1994, between about 00:55 and 01:50 (UTC+2) as the ship was crossing the Baltic Sea, en route from Tallinn, Estonia, to Stockholm, Sweden. Estonia was on a scheduled crossing with departure at 19:00 on 27 September. She had been expected in Stockholm the next morning at about 09:30. She was carrying 989 people: 803 passengers and 186 crew. Most of the passengers were Scandinavian, while most of the crew members were Estonian (several Swedish passengers were of Estonian origin). The ship was fully loaded, and was listing slightly to starboard because of poor cargo distribution.
At about 01:20 a weak female voice called "Häire, häire, laeval on häire", Estonian for "Alarm, alarm, there is alarm on the ship", over the public address system, which was followed immediately by an internal alarm for the crew, then one minute later by the general lifeboat alarm. The vessel's rapid list and the flooding prevented many people in the cabins from ascending to the boat deck. A Mayday was communicated by the ship's crew at 01:22, but did not follow international formats. Estonia directed a call to Silja Europa and only after making contact with her did the radio operator utter the word "Mayday". In English, the radio operator on Silja Europa, chief mate Teijo Seppelin replied: "Estonia, are you calling mayday?" After that, the voice of third mate Andres Tammes took over on Estonia and the conversation shifted to Finnish. Tammes was able to provide some details about their situation but due to loss of power, he could not give their position, which delayed rescue operations somewhat. Some minutes later power returned (or, somebody on the bridge managed to lower himself to the starboard side of the bridge to check the marine GPS, which will display the ship's position even in blackout conditions), and the Estonia was able to radio their position to Silja Europa and Mariella. The ship disappeared from the radar screens of other ships at around 01:50, and sank at 59°23′N 21°42′E in international waters, about 22 nautical miles (41 km; 25 mi) on bearing 157° from Utö island, Finland, to the depth of 74 to 85 metres (243 to 279 ft) of water. According to survivor accounts the ship sank stern first after taking a list of 90 degrees.