Since ancient times, from the Roman Empire around the Mediterranean Sea to floating islands used by the Uro people of Peru, civilisations have settled near water. Today, rising sea levels place coastal cities under constant threat. An estimated 250 million people currently live on land below projected annual flood levels, often in coastal cities such as London, Lagos, Mumbai or Shanghai; and this number may rise to 630 million by the end of the century. An additional 318 million people have been displaced since 2018, due to climate disasters. Many of these cities have already taken measures to adapt to rising sea levels. Shanghai is protected by a gigantic protection system, while New York City has created a system to shield its island-located economic borough of Manhattan. The government in Indonesia took one of the most drastic actions, deciding to move its entire capital inland, mainly because it was sinking and experienced regular flooding. The location of the new capital, Nusantara, has been criticised for leading to the displacement of indigenous populations and the destruction of vast areas of natural rain forest, essential to counteracting climate change. Could it be that, instead of humankind fleeing from water, building on it could serve as a better long-term solution? What would the creation of entire water cities entail for societies, economies and the environment? What if populations could live on water instead of facing displacement and migration? The combined effects of climate change, land subsidence and accelerated urbanisation could force us to rethink the use of water surfaces on Earth as potential settlement areas, as an alternative to an Earth surface made uninhabitable by over-population and climate catastrophes.