At 225,000 gross tonnes, Oasis of the Seas, one of two identical ships recently built for Royal Caribbean cruises, is 70,000 tonnes more and 21 metres longer than the previous record holder, Freedom of the Seas. By contrast, the Titanic, built by White Star Line nearly a century ago and at the time the largest steam ship ever, measured 269 metres and was less than a fifth of the size of today’s behemoths.