Cunard's Queen Mary 2 - Cunard's Queen Mary 2, featuring 17 decks and towering 62 metres (200 ft) above the waterline, one and half times higher than the Statue of Liberty, only 35 metres shorter than the Empire State Building. Click the pic for more on the Queen Mary and Queen Mary 2. Gross Registered Tonne (GRT) is 100 cubic feet. It is a measurement of space, not weight. The Queen Elizabeth was the longest cruise liner when she was launched in 1938, at 314 metres (1030 ft). She was destroyed in a fire while being renovated in Hong Kong harbour in 1972. The biggest ship in the world, the oil tanker Jahre Viking, is 458 metres (1,502 ft) long. A big oil tanker ships about 132 million litres (34 million gallons) of petrol. Enough to drive a car 47,000 times around the earth.