As the previous post mentioned, the conflict is between Ralph who is angry that the fire was not kept going, and Jack who felt that going to hunt was more important.  But it is also symbolic for the things that they are both representing.  Ralph is concerned for the future and knows that strict organization is the best way to take care of things like shelter and a signal fire but Jack knows that the boys are hungry and that the hunt and the fire and the meat will please them immediately.  The hedonistic allure of the hunt and the meat wins over so many of the boys that eventually it is only a fire set to smoke Ralph out of hiding that brings a ship to the island.

The boys built a fire on top of the mountain to signal any passing ships of their presence on the island. Jack and his men were supposed to make sure that the fire remained ablaze, but Jack decided to go on a hunt for a pig instead. His excuse - they had to eat. This angers Ralph because he saw the ship and then realized that the fire has gone out and they would not be rescued. The ship represents the return to civilization for the boys and the hunt represents a return to the primitive life for the boys. this scene foreshadows what happens between Ralph and Jack - the clash between civilized man and primitive man.

Why is Ralph so angry with Jack after spotting the ship, and what is Jack's excuse?

In Chapter 6 of "Lord of the Flies,"Ralph, the voice of civilization is angered that the fire has gone out while the boys run around the island looking for the "beast."  He turns to the assembly of boys and asks them, "Don't you all want to be rescued?" With the support turning to his side, Ralph then asks Jack if there is anywhere on the island that he has not been.  Jack answers "unwillingly" as he is disgruntled that Ralph has regained his leadership. For, earlier Jack had dominated Pippy by "contemptuously" accusing Piggy of always being scared. Also, he contended that the conch was not needed anymore, and "it's time some people knew they've got to keep quiet and leave deciding things to the rest of us...This is a hunter's job."

At this point Jack strives to usurp Ralph and Piggy's power as the civilized and intelligent leaders of the group.  He talks of rocks and rocks making good bridges.  The rock, a symbol of the Stone Age, suggests the rising savagery in Jack and the hunters, especially the innately sadistic Roger.  Here Golding writes that

Simon thought of the beast; there rose before his inward sight the picture of a human at once heroic and sick.

In the lagoon, the "sleeping leviathan breathed out...and the water boiled over the table rock with a roar."  This passage foreshadows the rise of the strong savage nature in the boys--"[the]long fall and rise and fall [of the waves]"--and their vicious acts of destroying Simon and Piggy,just as the "leviathan," Moby Dick, Melville's evil force, drowned Ahab--he,too, once heroic and sick--in the long fall and rise of the ocean waves.