Aquapolis. Free city building!

The events in the game begin from the moment you return to Earth after a year's space expedition. Since your spacecraft's antenna was faulty, communication between the spacecraft and the planet was not maintained. But, flying closer to the globe, you suddenly find that the entire land for some reason was covered with water. At the bottom of the ocean, you have to meet intelligent creatures living in the underwater world, and try to solve the riddle of what happened to humanity and the planet.