The oceanic world is so beautiful, however, it is dangerous as well. You will find yourself in a hostile and dangerous environment where surviving is a real challenge, because your city is located on the surface of the water, that is way it can disappear in any moment. And this is something you need to prevent no matter how hard it will feel. You need to find water and water for the city dwellers and catch and remove the trash that flows in the water around. Try to build a water-civilization and keep it alive for a long time.