Voyage Diary, Secret Voyage to the Sea

In 2300 AD, mankind experienced a hundred years of extreme climate collapse. The ice caps of the Arctic and Antarctic completely melted, and the sea level rose by more than 100 meters. Ninety percent of the world's coastal cities have sunk into the sea, and all former cities have been reduced to underwater ruins, which are called "sinking ruins" by later generations. Only the remaining settlements in the plateau and mountains are left on the land. The population has dropped sharply, and the industrial civilization has retreated. Half of the technology of the old era has expired, and satellite navigation has completely failed due to geomagnetic disorder. Humanity has returned to the era of stargazing to identify positions and weather navigation. The sea is no longer a transportation carrier, but a forbidden area that swallows everything: strange magnetic storms, mutated sea beasts, foggy areas, and no-signal blind spots are everywhere. Human beings huddled in the only remaining highland city-states, fearful of the sea, and no one ever sailed far. The world acquiesces: there is only death in the sea and no truth.