great sea: i.e. the Mediterranean, a modern name for the Great Sea.
point out = mark out or claim. Hebrew. ta'ah. Occurs only here.
mount Hor. Not the mount Hor where Aaron died, which was in the south corner of Edom (Num_33:37, Num_33:38), but another, in the north, mount Hermon, a spur of the Lebanon (Jos_13:5). Hermon had several names. Compare Deu_3:9; Deu_4:48.