How would cities and other such structures be assembled by nonterrestrial animals that do not have access to a solid foundation? Would it even be plausible for this to happen? I’ll focus on pleustonic species, which seem as a microcosm of the issues in these species
I’d say pleusters could build boats, or even ships, given the right materials. Being pleuston, they would easily be able to derive sustenance out of the water. When needed, this could be extended to a sort of agriculture using nets and frameworks to grow and cultivate their food