To proceed to the next sea or unlock new locations or chapters in Idle Arks, you must achieve all the stars or finish the ark upgrades. To do that, you will have to build all sorts of structures on all the floors. On the bottom-right corner, tap the “crafting” hammer button -> on the next screen, you will see all the things that you can build. Switch to other floors and complete the construction.
Once you are all done, you will get to sail. Keep sailing and unlock all the locations. As of now, the game features these locations; lost temple, red and sand, odyssey. In each location, there would be different ark missions to complete.