While surveying the bottom of the Baltic Sea, a gas line company has discovered a dozen sunken ships – some of which are incredibly well preserved.

The Wheel of a ship that could be from an 18th or 19th century lays at the bottom of the Baltic Sea (Courtesy: Nord Stream)

The oldest of the ships dates back to medieval times and could be as much as 800 years old. Most of the ships though, are commercial ships from between the 18^th and 19^th centuries, the Swedish National Heritage Board spokesperson, Peter Norman said in a media release.

"They could be interesting, but we have only seen pictures of their exterior,” Norman told The Associated Press. “Many of them are considered to be fully intact. They look very well-preserved."

The Baltic Sea is notorious for preserving sunken ships because of its unique biology – it lacks a ship worm that degrades wood.

Preliminary analysis indicates at least nine of the 12 ships are of great cultural and historical value, the Swedish National Heritage board said in a statement. They’re currently in the process of registering the shipwrecks as permanent ancient monuments.

The ships were found in an area east of Gotland Island – a Swedish island south of Stockholm – Nord Stream's spokesperson, Tora Leifland Holström told TheDailyPlanet.com.

They were discovered in an area 48 kilometres long by 2 kilometres wide. The 96 square kilometre area is approximately the same size as Paris, France.

Pictures of the site show that three of the ships still have intact hulls and are laying upside down, approximately 130 metres below the sea. The Heritage board is particularly interested in what might be contained in the ships.

“The content can tell us a lot about everyday life during that time," Norman said.

Whether or not the ships will be salvaged is still unlear, but the Heritage Board hopes they’re explored and the contents uncovered by divers. They note though that due to deep waters, diving could be costly.

Nord Stream is gearing up to start the construction of the pipeline this April. They said they’d accommodate operations so that they don’t affect the site.

By the time Nord Stream finishes the pipeline, nearly 2,500km of it will have been laid between Russia and Germany.  Two parallel lines will each have the capacity to transport 27.5 billion cubic metres of natural gas, with a total capacity of 55 billion cubic metres per year.  The first of the two lines will be completed by 2011.