Apparently, one of the guys in the design office was asked for a quote for advertising by the ad company and he said 'Well, in our opinion it is virtually unsinkable'. The advertising company decided to drop the 'virtually'.
As an aside, I was on a cruise on the Celebrity Eclipse (new cruise ship that you may remember went to 'rescue' some holidaymakers stranded by the ash cloud in April). Anyway, during one of the trivia quizzes the question was (and I may get my numbers a bit wrong) "the Titanic had 12 watertight compartments and would sink if 4 were flooded. The Eclipse has 14 compartments. How many need to be flooded for it to sink?". Well, of course everyone thought what with advances in technology etc that answer must be at least half...say 7 or 8. Answer was 5, so hardly better than the Titanic!