So, if I have a ship model is here, if this is the water level, if I moved it at a constant speed, its resistance will act opposite, horizontally and the entire total resistance will have a centroid somewhere in the middle where the resistance will act this way- am I right? Yes, the resultant you can easily calculate if you take moments of the individual resistance components and calculate then, you should get this thing if you know at each section what is the range, if you know- we do not know- but roughly it will be somewhere in the middle of the length of the ship and somewhere in the middle of the draft or may be slightly lower, because the bottom portion will come.