OFMG, Melville basically tells us straight out what he's doing on goddamn page 4-5! Look:
"…meditation and water are wedded forever … Narcisuss, who because he could not grasp the tormenting, mild image he saw in the fountain, plunged into it and was drowned. But that same image, we ourselves see in all rivers and oceans. It is the image of the ungraspable phantom of life; and this is the key to it all."
And of course everyone drowns except Ishmael, whatever that means, though I suppose if I think about it then I'll just drown in Moby Dick myself. Scholarship as suicide, as another alternative to pistol and ball, heh.