After the Great War against the Dalki, the planet Earth lost most of its landmass, leading to a significant rise in water level and even less land for the populace to live on. To resolve this problem, Logan built a city above the sea, and the Pure came up with a different solution.
Cruising through the waves as if they were nothing was a gigantic city on a ship. It was enormous, as if someone had attached ten battleships and built a city on them. On top of that, there were more ships around it, ahead, to the left, to the right, at the front and behind. And all of them were moving at the same and constant speed to protect the large ship at any point and time.