According to a quotation by Reynolds and Sjodahl,
‘Sir Isaac Newton observes that to the Hebrews the continents of Asia and Africa were “the earth,” because they had access to them by land, while the parts of the earth to which they sailed over the sea were “the isles of the sea.”’
(Commentary on the Book of Mormon, 1:214.)
Thus, Nephi not only refers to the isles of the sea as the location of other remnants of the house of Israel, but he also indicates that he and his people were then living upon an ‘isle of the sea’ when he quite clearly is referring to the great land mass known as the American continent. (2 Nephi 10:20–21.)
(Daniel H. Ludlow, A Companion to Your Study of the Book of Mormon, p. 121)