[L]ulled into such an opium-like listlessness of vacant, unconscious reverie is this absent-minded youth by the blending cadence of waves with thoughts, that at last he loses his identity; takes the mystic ocean at his feet for the visible image of that deep, blue, bottomless soul, pervading mankind and nature; and every strange, half-seen, gliding, beautiful thing that eludes him; every dimly-discovered, uprising fin of some undiscernible form, seems to him the embodiment of those elusive thoughts that only people the soul by continually flitting through it. In this enchanted mood, thy spirit ebbs away to whence it came; becomes diffused through time and space; like Wickliff's sprinkled Pantheistic ashes, forming at last a part of every shore the round globe over. (Chapter 35)

Basic set up:

Ishmael, one of the protagonists of the novel (and sometimes its narrator), is staring out at the ocean and getting lost in all those blue waves.

The characters in Melville's Moby-Dick are surrounded by nature. After all, they're on a ship, and all around them is nothing but the deep, blue sea.

Because of this fact, nature is a huge theme in the novel, and Melville evokes it in beautiful ways, as in the scene above. We see the "cadence of the waves," the "uprising fin[s]" of strange creatures, and the huge immensity of the ocean surrounding our boy Ishmael.

This passage not only gives us a very evocative description of the ocean, it also presents the ocean as symbol (we told you those American Romantics were really into symbolism). The sea becomes the "image" of the soul in the passage above. The creatures that inhabit it are like those "elusive thoughts" that inhabit the soul. Deep, bro.

In other words, there's a lot of nature and a lot of symbolism going on in this excerpt. The description of the ocean melds into the description of the soul, and nature is represented as embodying the human soul.