The Book of Mormon refers to the Atlantic Ocean as the “Great Deep” “Great Water” “Irreantum” “Many Waters” and “Deep”:
17 And when my brethren saw that I was about to build a ship they began to murmur against me saying: Our brother is a fool for he thinketh that he can build a ship; yea, and he also thinketh that he can CROSS THESE GREAT WATERS. (1 Nephi 17)
16 And they journeyed in the wilderness and were brought by the hand of the Lord ACROSS THE GREAT WATERS into the land where Mosiah discovered them; and they had dwelt there from that time forth. (Omni 1)
22 Behold O Lord, wilt thou suffer that we shall CROSS THIS GREAT WATER in darkness? (Ether 2)
3 And thus the Lord caused stones to shine in darkness, to give light unto men, women, and children, that they might not CROSS THE GREAT WATERS in darkness. (Ether 6)
10 And it came to pass that I looked and beheld MANY WATERS; and they divided the Gentiles from the seed of my brethren.
12 And I looked and beheld a man among the Gentiles, who was separated from the seed of my brethren by the MANY WATERS; and I beheld the Spirit of God, that it came down and wrought upon the man; and he went forth upon the MANY WATERS, even unto the seed of my brethren, who were in the promised land.
13 And it came to pass that I beheld the Spirit of God, that it wrought upon other Gentiles; and they went forth out of captivity, upon the MANY WATERS.
29 And after these plain and precious things were taken away it goeth forth unto all the nations of the Gentiles; and after it goeth forth unto all the nations of the Gentiles, yea, even across the MANY WATERS which thou hast seen with the Gentiles which have gone forth out of captivity, thou seest—because of the many plain and precious things which have been taken out of the book, which were plain unto the understanding of the children of men, according to the plainness which is in the Lamb of God—because of these things which are taken away out of the gospel of the Lamb, an exceedingly great many do stumble, yea, insomuch that Satan hath great power over them. (1 Nephi 13)
5 And we did come to the land which we called Bountiful, because of its much fruit and also wild honey; and all these things were prepared of the Lord that we might not perish. And we beheld the SEA, which we called IRREANTUM, which, being interpreted, is MANY WATERS. (1 Nephi 17)
3 Behold, O Lord, thou hast smitten us because of our iniquity and hast driven us forth and for these many years we have been in the wilderness; nevertheless thou hast been merciful unto us. O Lord, look upon me in pity and turn away thine anger from this thy people, and suffer not that they shall go forth ACROSS THIS RAGING DEEP in darkness; but behold these things which I have molten out of the rock. (Ether 3)
7 And it came to pass that when they were buried in the DEEP there was no water that could hurt them, their vessels being tight like unto a dish, and also they were tight like unto the ark of Noah; therefore when they were encompassed about by many waters they did cry unto the Lord, and he did bring them forth again upon the top of the waters. (Ether 6)
2 And it came to pass that Shez did remember the destruction of his fathers and he did build up a righteous kingdom for he remembered what the Lord had done in bringing Jared and his brother ACROSS THE DEEP and he did walk in the ways of the Lord and he begat sons and daughters. (Ether 10)
20 My God hath been my support; he hath led me through mine afflictions in the wilderness; and he hath preserved me upon the WATERS OF THE GREAT DEEP. (2 Nephi 4)
10 Art thou not he who hath dried the sea, the WATERS OF THE GREAT DEEP; that hath made the depths of the sea a way for the ransomed to pass over? (2 Nephi 8)
16 And behold, also, if he say unto the WATERS OF THE GREAT DEEP—Be thou dried up—it is done. (Helaman 12)
25 And behold, I prepare you against these things; for ye cannot CROSS THIS GREAT DEEP save I prepare you against the waves of the sea, and the winds which have gone forth, and the floods which shall come. Therefore what will ye that I should prepare for you that ye may have light when ye are swallowed up in the depths of the sea? (Ether 2)
27 And there were no more wars in the days of Shule; and he remembered the great things that the Lord had done for his fathers in bringing them ACROSS THE GREAT DEEP into the promised land; wherefore he did execute judgment in righteousness all his days. (Ether 7)
9 Now the daughter of Jared was exceedingly fair. And it came to pass that she did talk with her father, and said unto him: Whereby hath my father so much sorrow? Hath he not read the record which our fathers brought ACROSS THE GREAT DEEP? Behold, is there not an account concerning them of old, that they by their secret plans did obtain kingdoms and great glory? (Ether 8)
AT NO POINT IN TIME ARE THESE TERMS USED TO DESCRIBE THE WATERS THAT BORDER BOOK OF MORMON LANDS.
BOOK OF MORMON LANDS WERE HIDDEN
Book of Mormon lands were hidden, not directly connected to the Great Sea:
8 And behold it is wisdom that this land should be kept as yet from the knowledge of other nations for behold many nations would overrun the land that there would be no place for an inheritance. (2 Nephi 1)
The Liahona had to be used to find them:
12 And it came to pass that after they had bound me insomuch that I could not move the compass which had been prepared of the Lord did cease to work.
21 And it came to pass after they had loosed me behold I took the compass and it did work whither I desired it.
22 And it came to pass that I Nephi did guide the ship that we sailed again towards the promised land. (1 Nephi 18)
The Great Sea does not border Book of Mormon lands. Early explorers (e.g., Columbus) would NOT find Book of Mormon lands right off the bat. Nor would they bring an oppressive religion from which the Gentiles were fleeing with them.