Anime with royalty fighting in airships

Question

I am trying to find the name of an anime I saw many many years ago. The story was built around a war between two parties. The battles were fought up high, in big airships. One particularity was that each ship would open a hatch where a group of soldiers were standing to shoot what looked like basic muskets.

There was a supreme ruler of the world who abused his power and was pitting the two factions against each other.

There was also a scarcity of water in the world. As a citizen you could get 4th water, 3rd water and so on, but the supreme ruler had a whole lake of first water.

Answer 1

This sounds like Last Exile. See their wiki for a description of First Water:

First Water is clear enough to see through and clean enough to drink without first being boiled. Because Anatoray exists in an arid desert, First Water is rare, and treated as a commodity. For people of the lower classes, even Third Water can be a rare treat. The Guild, however, has enough access to First Water to use it frivolously, such as for washing the mud off a catfish.