The earth is overpopulated. The colonization of the planet Mars is still four decades in the future. There is only one path that human expansion can still take: that to the bottom of the sea. The players compete to build the greatest underwater nation - an archipelago of submarine cities connected by a network of transport tunnels. Seaweed farms and desalination plants will provide your people with food and fresh water. Laboratories will provide you with the knowledge you need to run everything as efficiently as possible. You may even be able to build symbiotic cities that fully integrate into the submarine ecosystem. You start with a single city, expand your network and connect it to the coastal metropolises. In times when hunger exceeds agricultural yield and water scarcity puts pressure on the confederation, you will create a nation that will be self-sufficient and one day even be able to sell its products to those who stayed on land.