> are equally meaninglessly > large to any lay reader. No, because a cubic kilometer of ocean does not contain a nice round number of liters of water. It

> are equally meaninglessly > large to any lay reader. No, because a cubic kilometer of ocean does not contain a nice round number of liters of water. It contains however many liters of water are in that cubic kilometer after you subtract everything else in the ocean, it'll be close to a trillion liters, but not quite. Of course the article may be using "water" in the loose sense. But if it's not the metric version would implicitly provide you with an easily inferred percentage of how much of a cubic kilometer of ocean is made up of other stuff. Whereas in imperial units you won't know that at a glance, you'll need to either repeat the calculation, or memorize various conversions.