Joel 2:20; Ezekiel 47:18. Literally, the front sea, i.e. the Dead Sea, which one looking E. would face; "the utmost (hinder) sea" is the Mediterranean, at such a one's back (Numbers 34:6).
Bibliography Information Fausset, Andrew Robert M.A., D.D., "Definition for 'East sea' Fausset's Bible Dictionary". bible-history.com - Fausset's; 1878.