Ok I got it wrong. The fact was that 15 of the worlds biggest ships emit as much pollution as the entire worlds 760,000,000 cars.
I think that is an even more impressive statistic than the whole of the UK one anyway.
/Goes and boils a full kettle for 1 cup of tea and turns the thermostat up a couple of degrees...
Ships use the last dregs of the oil after all the otherwise useable stuff has been removed, that means its very high in sulphur, which is bad for the environment, producing nasty effects on health and acid rain. Carbon wise its about the same as burning tar.