An iron hulled ship is sailing due north. Help with a physics question?

The first thing is if the ship is pointing north (sailing) then the bow of the ship is the south pole because opposites attract. The second thing is that magnets if individual when put together then add together and as a result of this then the field strength over the length of the ship will be a gradient from max at one end to zero at some point near the middle to another max at the other end all be it the opposite pole to the preceding end. This is also uming that the ship is not influenced by wind, current (in the ocean) and being steered by a person. By person i mean that it is possible to make a ship that has its own magnetic poles go against the way it would naturally lie within the Earths magnetic poles, in the same way we put two magnets together with north poles facing each other and overcome the force of repulsion with a stronger force. This is the best i know of this, not to say that i am correct.