THE WORLD'S biggest cruise ship has felt the sea underneath her for the first time at a milestone float-out ceremony in Finland.

The 220,000-tonne leviathan, called Oasis of the Seas, is being built by American company Royal Caribbean at the STX Europe shipyard in Turku.

The 1,187ft vessel, which can carry 6296 passengers, is so big that its exhaust stack retracts so it can pass under bridges as it travels the world.

Representatives from the owners and the shipyard turned a wheel to let the water into the enormous dry dock where the 65% finished vessel is still being built.

It takes about 15 hours to fill the dock as it needs 87 million gallons of water to float the ship.

The £700 million vessel is 40% bigger than any other cruise ship afloat and it has a Central Park-style open-air space aboard the size of a football field with its own micro-climate.

The world-first attraction means that guests can have the option of a sea or tree view.

In addition there is a bar called Rising Tide that will move between three of the 16 passenger decks. Completing the major new attractions is a 750-seat AquaTheater concept, modelled on an ancient Greek amphitheatre, located at the stern of the ship.

The ship, which will be completed next year, is also family-friendly, with activities including surf machines and a climbing walls as the company tries to lure younger people to cruise.

Oasis is due to go on its first cruise in December next year, operating from Fort Lauderdale in Florida. Prices will start from £1,299 for nine-night eastern Caribbean fly-cruise.