The first stories that men shared happened on water. The seat of civilizations were founded there, on rivers and ports, and their navies spread influence far and wide. The Phoenicians consolidated the alphabet from ships. The Mediterranean shaped Homer's great epics. The Judeo-Christian tradition used water to take away life (the Red Sea, The Flood, Jonah) and later to give life (baptism). The two greatest novels in American literature (Moby Dick and Huck Finn) are set on water, which stands apart from the inequities of law on land. In short, the sea gives rise to land-based man's sense of wonder and tests the limits of his knowledge, and the leviathan's world beneath sends men forth on epic journeys, only later to punish their hubris. And let us not forget that Melville, like Ishmael, had no money for proper schooling, and so too was drawn to the sea and educated on a vessel.
In my edition of Moby Dick, "water" is mentioned 291 times, 10 times in chapter 1. In addition, the "sea" is mentioned 719 times in the novel, 17 times in chapter 1. By contrast, "love" is mentioned only 46 times in Moby Dick; "God" only 185 times; "women/woman" only 21 times. So, it is clear that the watery world not only permeates the novel as theme, symbol, and motif, but it dominates the Moby Dick as setting and character. In the novel, the sea is another world: the world of men and beast, not of God or or love or women. Melville makes these distinctions in chapter 1 by saying that, for a young man, all roads and paths lead to water:
Right and left, the streets take you waterward.
All men's eyes lead out to sea:
Posted like silent sentinels all around the town, stand thousands upon thousands of mortal men fixed in ocean reveries.
Ishmael says the sea is cure for his "hypos" (anger, melancholy), for death (it prevents him from bring up the rear of funerals), for the "damp, drizzly November in my soul," for his lack of money, for his need for education and adventure, and for his need for camaraderie. He makes it clear that he goes to sea neither as a passenger (as that requires money), nor as an officer or cook (as that requires skill), but as a simple sailor. As a reader, we can tell that Ishmael is an observer and a pilgrim, unlike his epic Greek predecessors (Odysseus), that he wants to be reborn at sea (the sea is the Spring to cure death and his November doldrums). At its heart, Ishmael's quest is spiritual.
At the end of the chapter, Ishmael admits the he wants to see the great whales, creatures that in the 19th Century gave light (sperm oil) to the lamps of those on land. Metaphorically, whales were gods, once kin to man, as they inhabited the mysterious depths and yet had to surface for breath. Melville (like Darwin) must have seen their relationships to man, that whales were once land creatures who took to the seas for survival. What separated whales from men was that they could explore the depths of the sea (know the depths of knowledge). This theme of knowing what is beneath the surface made the watery world of the whale the perfect metaphor for Ishmael to chase.