Sea Diamond was built as the ferry Birka Princess, for Birka Line, by the Finnish state-owned company Valmet, at their Vuosaari shipyard in Helsinki and delivered in 1986. She sailed on 24-hour booze-cruises between Stockholm and the Åland Islands in Finland. Between 1990 and 2003 she also made longer cruises around the Baltic during the summer season. As built, she had a small car deck, with space for 80 passenger cars. Like most cruise-ferries in the Baltic, she was built to ice class 1A.
Birka Princess as built was 21,484 GT; 460 feet long, with a beam of 81 feet. Twin screw, powered by four Pielstick diesel engines, producing 24,000 bhp, providing a service speed of 18 knots. She had accommodation for 1,394 berthed passengers in one class, with a crew of 150.
In 1999 she was extensively refitted at Lloyd Werft in Germany, when the fore superstructure was extended and streamlined and 62 new passenger cabins were added, including a new deck of cabins above the bridge. In October 2004, when the new Birka Paradise was delivered, the Birka Princess started making two-night cruises from Stockholm to Turku, Helsinki and Tallinn, as well a weekly 24-hour cruise from Stockholm to Mariehamn. The new itineraries proved largely unsuccessful and on 2 January 2006, the ship was laid up in Mariehamn and offered for sale.
In February 2006 she was sold to the Cyprus-based Louis Cruise Lines. As built, the ship only had an indoor pool, in the sauna section on deck 2 in the bow of the ship. A new outdoor swimming pool was installed and the sundeck area increased, at Turku Repair Yard, Naantali. The heavily modified ship re-entered service in the Mediterranean as Sea Diamond.
On April 5, 2007, at around 16:00 EEST the ship ran aground, on a well-marked volcanic reef east of Nea Kamei, within the caldera of the Greek island of Santorin, began taking on water, and listed up to 12 degrees to starboard before her watertight doors were reportedly closed (a report which was later refuted when the wreck was examined).The 1,195 passengers, mostly Americans and 60 Canadians, were initially all reported to be safely evacuated in three and a half hours, with four injuries. Some passengers were evacuated from the car ramp, through the former car deck onto boats, but some passengers had to climb down rope ladders from the higher decks. Later, it was reported that two French passengers, occupying a cabin on the lowest passenger deck were missing.
The ship was towed off the rocks, and an unsuccessful attempt made to stabilize her list. The large amount of water taken on board led to the ship sinking shortly before 19:00 on April 6, 2007, only a few hundred metres from the shore. Video footage shows that, toward the end, the ship capsized before settling stern first onto the sea floor. It was later reported that the tip of the bulbous bow was only 62 metres below sea level, but the stern was in water up to 180 metres deep. It is feared that the wreck would soon slide deeper and sink into the submerged caldera of the volcanic island. It has been speculated that the deep, almost vertical shore of the bathtub-like caldera made it impossible to beach the ship and save her from becoming a total loss.
On April 7, Greek authorities announced that they were charging the captain and five other officers with negligence. State television reported they were charged with causing a shipwreck through negligence, breaching international shipping safety regulations and polluting the environment. Additional charges could be made, depending on the fate of the two missing passengers. All six were released until further notice, but if convicted they could face a five-year prison sentence.
Investigations carried out by the defence team for the master of the vessel and Louis Cruise Lines, included a new hydrographic survey of the area of the accident in Santorini. This survey discovered discrepancies between the actual mapping of the sea area and the official charts used by the Sea Diamond (and all other vessels) at the time of the accident. The detailed survey revealed that the reef, which the Sea Diamond struck, is in fact lying at 131 meters from shore and not at a distance of 57 meters, as is incorrectly marked on the Greek charts. The official chart also shows the depth of the water at the area of impact varying from 18-22 meters, whilst the recent survey shows that it is only 5 meters. Nevertheless the first official enquiry blamed the Sea Diamond’s captain for the loss, by taking a course much nearer the shore than the other cruise vessels that call at Santorini.