The ocean is a major symbol in Nausea. Its presence allows Sartre to interrogate ideas about surface appearance versus internal realities. After his lunch with the Self-Taught Man, Antoine wanders the city in a daze until he comes back to the seafront. He observes other people watching the ocean and admiring its green surface, “delicate colours, delicate perfumes,” and the “souls of spring” (124). Antoine believes that the green sea that the others observe is an illusion. He writes, “The true sea is cold and black, full of animals; it crawls under this thin green film made to deceive human beings. […] I see beneath it! The veneer melts […]” (124). The “thin green film” of the ocean’s surface is its essence: People see it and decide that it encapsulates the existence of the ocean. The ocean’s actual existence, however, has little to do with the surface that humans see. The ocean is full of “shining velvety scales” that “split and gape” (124). Antoine’s grotesque description of the sea suggests that the “true sea” is innately antithetical to the pleasant, green surface that the Bouville citizens admire.

The ocean is a symbol of the tension between the novel’s ideas of existence and essence.