Read Joshua 15:12 Using Other Translations
And the west border was to the great sea, and the coast thereof. This is the coast of the children of Judah round about according to their families.
And the west boundary was the Great Sea with its coastline. This is the boundary around the people of Judah according to their clans.
The western boundary was the shoreline of the Mediterranean Sea. These are the boundaries for the clans of the tribe of Judah.