In Lord of the Flies, each chapter carries a title which gives the reader insight into significant aspects of the book and the development of the plot. The first chapter, The Sound of The Shell, introduces the reader to a seemingly idyllic environment where, at this stage, the reader is oblivious to the importance of the shell in determining who will be chief - Ralph, with "the trumpet-thing."
Each chapter then adds more momentum. Chapter 2, Fire on the Mountain, already indicates to the reader that there is trouble in Paradise and, in fact, "a tree exploded in the fire like a bomb." Chapter 3, Huts on the Beach suggests a more relaxed chapter as the boys adapt to their environment, especially after their disastrous attempts at creating a signal fire and this is extended in Chapter 4, Painted Faces and Long Hair, as it is becoming apparent, from the chapter title that the boys are becoming less civilized. What is not apparent from the chapter titles but will become so in chapter 5, is the emergence of "the beastie."
The title "Beast From Water," is significant as the story will develop quite dramatically from here as, as remarked by Ralph, "things are breaking up." The boys are becoming increasingly opposed to any form of leadership and obeying the rules that Ralph and Piggy have created is difficult, in fact jack is quite vocal as he expresses himself. The boys are also frightened and Jack's impatience and name -calling, as he accuses everyone of being, "cry-babies and sissies," only serves to increase the fear, as "The vivid horror of this, so possible and so nakedly terrifying..." The "snake-thing" has now developed and is no longer even a diminutive "beastie," but is "a beast." Therefore, the title of this chapter is crucial and foreshadows what will, ultimately, contribute to the tragedy that awaits both Simon and Piggy and "the end of innocence."
In chapter 5, "Beast from Water," the fears of the boys are discussed openly in a meeting. Unfortunately, Ralph has called the meeting just at dusk, and by the time he opens up the discussion to the "beast" that some children have been talking about, the island has become dark. First, the older boys assure the littluns that there cannot possibly be a beast, that is, a creature, on the island. The hunters as well as Piggy and Ralph have explored pretty much the entire island, and they all assure the boys that a large, threatening animal could not be living there.
However, just as the boys are reaching a place of assurance, little Percival, the most fearful of the children, states that "the beast comes out of the sea." This is a terrifying thought because it presents a distinct possibility. Maurice, an older boy, rises to speak and brings science to bear on the subject, insisting than all the ocean creatures have not yet been discovered. This emphasizes the vulnerability of the boys on the island; they are surrounded by a wide ocean and would have no way to protect themselves from such a threat. Simon rises to try to focus the discussion not on imaginary threats, but on what he alone has discerned is the true threat, stating about the beast, "maybe it's only us." That answer receives scorn, but it leads to another boy suggesting the possibility of ghosts, and in the eerie darkness, the boys begin to entertain that suggestion. The assembly breaks up, leading Ralph to question his own leadership.
The "beast from water" represents the boys' nameless fears. The next chapter, "Beast from Air," symbolizes a closer, more tangible, and greater threat, the threat of violence and war. Both of these are external representations of the true "beast," which, as Simon tried to suggest early on, is the moral darkness within the boys themselves.
This occurs during a meeting in which Ralph is trying to keep order and control of the boys. Ralph is upset that nothing is getting done, and he wants to impress upon the boys the seriousness of their situation. The littluns are afraid of the beast, and Ralph and Piggy believe if they talk about it, it will show how silly their ideas of the beast are. At this meeting, Percival whispers to Jack that the beast comes from the sea, and this statement makes the beast all too real for the boys again. The boys think of the vastness of the sea and the numerous possibilities of what could exist in the sea, and this scares the boys all over again into believing that the beast exists.
During the chapter "Beast in the water" the boys become increasingly more savage, uncivilized, without rational thought, and will believe in things like "the beast" easier. The significance is that it represents the boys savagry just by not being literarily correct.