Why is the novel Frankenstein initially set aboard a ship?
The novel begins in a land of ice to contrast the Monster's birth by fire. The novel's early chapters (actually letters) are told by someone just like Victor, an explorer Robert Walton. Walton, then, is the outside narrator of a frame story who will bring Victor's inside story back to civilization. Walton writes his portion of the frame story as a series of letters to his sister.
Walton's letters chronologically take place near the end of the story. The explorer is on a sailing vessel seeking a passage to the North Pole, and he picks up Victor Frankenstein, who tells him his story. Victor and the Monster have chased each other to the land of ice, both seeking revenge against the other. Walton, then, is like us, the audience, in that we are hearing Victor's tale. Walton, who suffers the same hubris as Victor, must decide if he will push on and risk his life and the lives of men or turn back and return to the community of men (and his sister). The reader must make similar decisions. Victor's story will obviously try to persuade Walton and us to form communities, not seek personal glory alone.
Frankenstein stands as a relatively early novel, that literary form only beginning in the mid-1700's. The very first work of this "new form" (from which the Latin term "novel" comes) is considered to be Pamela, or Virtue Rewarded, written by Samuel Richardson (1689-1761) and published during the 1740's. The work is comprised of a series of letters which embody the narrative. Most novels from that time forward were modelled after this structure; this makes sense in an era where literary people (meaning those who could read) were used to corresponding with each other through the mail. For them, reading a novel would be the experience of coming across someone's private correspondence. By 1818, when Frankenstein, or the Modern Prometheus was first published (written by Mary Wollstonecraft Shelley (1797-1851)) this convention of telling the narrative through letters, although still in force, was not the only method to convey a story. Being her first novel, however, she relies upon the classic standard method of introducing the novel to her readers.
One of the most desolate places on earth are the polar regions. Victor Frankenstein created a creature that was rejected and isolated from people due to his appearance. In the book "Frankenstein" the creature had the desire to be wanted by people. He needed the social interaction of others. Instead of getting it, people looked at him and became terrified. He was rejected by everyone including his creator.
The creature is a victim of his isolation and later his revenge. He commits violent crimes against people. In order to isolate himself from the cruelty of the human world he goes to the far reaches of earth. Victor knows he must destroy the creature. Victor travels by ship to the isolated place that can only be reached by ship and later by dog sled. The setting is necessary for the reader to get an understanding of the level of isolation that the creature lives within.