A2SEA was established in 2000. In 2001, M/S
Ocean Ady (now:
Sea Energy) and M/S
Ocean Hanne (now:
Sea Power) were converted into turbine installation vessels. The company's first installation work was the
Horns Rev 1 wind farm in the North Sea in 2002. In following years the company installed among others the Frederikshavn,
Nysted,
Arklow Bank,
Scroby Sands,
Kentish Flats and
Thanet, and got contracts for the installation works on
London Array and
Ormonde offshore wind farms. In 2009, the company was acquired by the Danish energy company
DONG Energy. In 2010, it was announced that
Siemens Wind Power will acquire a 49% stake in the company at a price of DKK 860m. which came on 13 October 2010. In 2010, turnover was 586m DKK, while profit was 86m. In 2017, A2SEA was sold to GeoSea, a Belgian offshore installation company member of the DEME Group. In 2019,
DEME decided to integrate all its offshore companies (GeoSea, Tideway and A2SEA) into DEME Offshore. ==Fleet==