First of all, if we only consider the balance of the hull, we only need to consider the swing (left and right swing and back and forth swing) on the X axis and Y axis. Because the length of the ship is much higher than the width of the ship, rolling is usually more serious than pitching. Therefore, in ship design, reducing roll will take precedence over reducing pitch. Usually, a qualified ship in rolling and swaying also means that it meets the requirements of pitching and swaying. Before carefully calculating the seaworthiness of the ship, the engineer must first ensure that the GM distance in the picture below is within 0.5m-8m. If GM is less than 0m, it is equal to capsizing, while if GM is too high, it will make the crew and passengers uncomfortable, damage the cargo and damage the hull structure. Generally speaking, the passenger's ship will have a relatively low GM distance (but if the GM is too low, the ship will capsize), because this will prolong the rolling period and passengers will feel "soft" when sailing. In contrast, too high GM will shorten the rolling cycle, causing passengers to feel "hard" when sailing. Therefore, whether in port or at sea, the crew must check the quantity of cargo and fuel carried on board and adjust the water level of ballast tanks according to the weight of cargo and fuel to ensure that GM can maintain a safe and comfortable position. Almost all shipwrecks in human history are caused by low GM. Please read the navigator here and remember the importance of GM. Never overload the ship or ignore the water level in the ballast tank. If your boss doesn't understand, you can explain it to him, which means ensuring life safety! Assuming that the GM of the ship is in a qualified state, the hull itself can maintain a certain degree of balance without assistance. At the same time, the underwater shape of the hull will also affect the balance of the ship in waves, and waves at different angles will cause the ship to shake to varying degrees. The design of underwater hull shape is actually a combination of art and science. At present, there is no general mathematical formula to create the hull with the best seaworthiness (at present, it is still up to human exploration and model test). Of course, in the process of adjusting the hull, it is troublesome to consider seaworthiness, resistance, size and tonnage at the same time. In hull design, the size/tonnage is->; Weight evaluation->; In ship design projects, the design cycle of seaworthiness/resistance usually consumes a large part of time. In addition to the hull, the rudder equipped with the ship itself can also help the ship keep balance during navigation with the help of the automatic operating system.