Now, you see, these four wave systems, we have seen bow wave, forward shoulder wave, aft shoulder wave and stern wave; these four wave systems will super impose on each other and they would make the total wave making resistance. For the time being let us consider just two wave systems- the bow wave and the stern wave, which are more prominent. Now, if a crest of the bow wave and a crest of the stern wave match, then we will have a bigger crest there at that point- am I right?- what is this effect? If the crest is on the, near the ship, if the crest is against the ship body, not far away, then the effect is pressure at those points will increase and therefore, the axial component of the force supporting motion will increase, do you understand this?