 The thing picked out by the primary intension of "water" could have been otherwise.For example, on some other world where the inhabitants take "water" to mean "watery stuff", but, where the chemical make-up of watery stuff is not H2O, it is not the case that water is H2O for that world.The "secondary intension" of "water" is whatever thing "water" happens to pick out in "this" world, whatever that world happens to be.