The Sea South is named because it was south of the Land Northward:
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)
Most modelers (99.9%) ignore the Sea South reference, as do they the Sea North. The .1% percent that don’t fail to correctly place it south of the Jaredite Land Northward. They place it south of the Land Southward instead. We are not told what was south of where Lehi landed because Nephi migrated north away from his enemy brothers Laman and Lemuel.
Current mind set accepts the pre-existence of native people in, on, or around Book of Mormon land. Those are “Lamanites by birth” which were distinguished from “Lamanites by choice.”
Amalickiah who was a Nephite by birth (Alma 49:25)
people of Ammon who were Lamanites by birth (Helaman 3:12)
I shall call them Lamanites that seek to destroy the people of Nephi (Jacob 1:14)
The Lamanites outnumbered the Nephites. There lands were “south” of Nephite lands. There was a distinct “Line of Possession” that separated the two groups.
line of the possessions of the Lamanites. (Alma 50:13, see also 9-11)
No doubt what was south of where Lehi landed was Lamanite land. Which explains where their large numbers came from for the different battles. Without a large land south of where Lehi landed, modelers are at a loss to explain where the large number of Lamanites were living.
A few modelers have established the ground rules for using or discarding the Sea South and North references:
The reference to north and south seas fits nicely into the Mesoamerican scene as part of a metaphor for the whole earth and was probably used in a metaphorical sense in the Book of Mormon.” (A Key For Evaluating Nephite Geographies by John E. Clark in FARMS Review: Vol. 1, Issue 1, pp. 20-70 A review of “Deciphering the Geography of the Book of Mormon” by F. Richard Hauck Provo, Utah: Maxwell Institute, 1989, p. 65)
I am convinced that the reference to a north sea and a south sea is devoid of any concrete geographical content. All specific references or allusions to Book of Mormon seas are only to the east and west seas. Any geography that tries to accommodate a north and south sea, I think, is doomed to fail. (Ibid.)
Wilson also raises the question of how the sea north and sea south fit with the Limited Geography Model (3b), a matter which has been fully analyzed by John Clark.(Clark, “Key for Evaluating,” 63–67) The north and south seas are mentioned only twice (Helaman 3:8; Alma 22:32), in a vague general sense. Clark rightly attributes these references to common ancient macrogeographical world-views of the earth surrounded by the primordial “ocean.” THUS THE MINOR AND VAGUE MENTIONS OF THE NORTH AND SOUTH SEAS REFER TO MACROGEOGRAPHICAL COSMIC WORLD-VIEWS OF SEAS SURROUNDING THE ENTIRE LANDMASS, RATHER THAN SPECIFIC IDENTIFIABLE BODIES OF WATER. (“Basic Methodological Problems with the Anti-Mormon Approach to the Geography and Archaeology of the Book of Mormon, William J. Hamblin, Journal of Book of Mormon Studies: Volume – 2, Issue – 1, Pages: 161-97, Provo, Utah: Maxwell Institute, 1993)
Despite such naysaying of the text, what can’t be ignored are the “seashore” references to the Sea South. The background for the following reference is that the Land of Moron was along the west side, by the Narrow Neck. If the enemy came from the north, the only way to escape would have been south to the Sea South and then east along its seashore, (the Narrow Neck was not an option):
11 And it came to pass that in the first year of Lib, Coriantumr came up unto the land of Moron, and gave battle unto Lib.
12 And it came to pass that he fought with Lib, in which Lib did smite upon his arm that he was wounded; nevertheless, the army of Coriantumr did press forward upon Lib, that he fled to the borders upon the seashore.
13 And it came to pass that Coriantumr pursued him; and Lib gave battle unto him upon the seashore.
14 And it came to pass that Lib did smite the army of Coriantumr, that they fled again to the wilderness of Akish.
15 And it came to pass that Lib did pursue him until he came to the plains of Agosh. And Coriantumr had taken all the people with him as he fled before Lib in that quarter of the land whither he fled.
16 And when he had come to the plains of Agosh he gave battle unto Lib, and he smote upon him until he died; nevertheless, the brother of Lib did come against Coriantumr in the stead thereof, and the battle became exceedingly sore, in the which Coriantumr fled again before the army of the brother of Lib. (Ether 14)
Additional supports are: the plains which existed on the south side of the Sea South also, and were described as the Line Bountiful, it being the preferred route for crossing the Land Southward. Why? Because the Sea South was a shallow inland body of water also called the “Sea that Divides the Land” (Ether 10:20) which divided the land the same way that a mud puddle divides a trail.
As the Sea that Divides the Land evaporated, it left behind flat plains on the north and on the south, thus the many references to “plains” on either side of it.
Any model lacking a Sea South, south of the Land Northward is false. Just as any model lacking a Sea North, north of the Land Northward is false. If said sea does exist in a model, it must be accompanied by plains on its north and south, or it’s false. See Lake Tonawanda page for this sea.