When Jacob taught his people, he described their situation this way: “We have been led to a better land, for the Lord has made the sea our path, and we are upon an isle of the sea” (2 Nephi 10:20). We know they were somewhere in North, South, or Central America, and so we certainly wouldn’t characterize their place as “an island”, but Jacob surely had no idea at this time of the size of their “island” that we call two continents. What he knew was that they crossed an immense ocean and found land big enough for them to dwell on, and that was enough for him to call it an island. It appears that their main cities in the Book of Mormon throughout their history were never far from the ocean, and so the sea played an important part in the geography and events of Nephites.
Although we don’t have a lot of information about the geography in general of the Nephite civilization, the text gives us a few clues that help us have a general sense of their position in relation to the ocean. Mormon mentioned several times the “sea west” and “sea east,” and he gave us this explanation about the geography of the land of Nephi (where the Lamanites were after the days of Mosiah I) and the land of Zarahemla (where Mulek landed and the Nephites after Mosiah I were): “The land of Nephi and the land of Zarahemla were nearly surrounded by water, there being a small neck of land between the land northward and the land southward.” From south to north the lands were Nephi, Zarahemla, Bountiful, and then the narrow strip of land which separated the land southward (where most of the Book of Mormon took place) with Desolation and the land northward (where the Jaredites were). All of these lands were between the east and west sea, and it was apparently “the distance of a day and a half’s journey for a Nephite” at the shortest point between the east and west sea (Alma 22:27, 32). So nearly all of the book took place in close proximity to the sea, with the wards making particular mention of being close to the ocean. For example, Amalickiah’s army was camped on the east seashore when Teancum slayed him and Mormon spoke of the Nephite army of his day being “in the borders by the seashore” near the city Desolation (Alma 51:32, Mormon 4:3). In the final battles of the Jaredites some of the events also took place on the seashore: “The army of Coriantumr did press forward upon Lib, that he fled to the borders upon the seashore” (Ether 14:12). In only one chapter is there any mention of a sea besides the western or eastern sea: “And it came to pass that they did multiply and spread, and did go forth from the land southward to the land northward, and did spread insomuch that they began to cover the face of the whole earth, from the sea south to the sea north, from the sea west to the sea east” (Helaman 3:8). I don’t think this meant they were completely surrounded by water, but there must have been some curvature of the land that led them to label a northern and southern sea.All of this of course is of little importance compared to the message itself of the Book of Mormon about Jesus Christ. Like others, many of whom have devoted much time to the study of the Book of Mormon geography, I would love to know exactly where these events took place. But we have no need for that knowledge in order to know that wherever it was, the events truly did happen. There were indeed cities of Zarahemla and Bountiful close to the ocean, and the resurrected Savior did indeed come to minister to the Nephites there.