The "sea" in the Bible symbolizes separation from God — chaos and the outer courts where humanity remained outside His presence. Christ's death removed that barrier spiritually, and the destruction of the temple in 70 AD reflected this truth, showing the sea was no longer needed.

Revelation 21 depicts the sea as removed entirely, signaling the full uniting of heaven and earth under God's presence. If the sea still existed today, it would mean humanity remains separated from God and Christ's work is incomplete.

Since the spiritual barrier was removed and the temple destroyed, the sea cannot remain, implying that Christ already returned in the first century as He promised in Matthew 16:28 to establish His kingdom. The vision of Revelation 21, therefore, is a fulfillment already realized, not a distant future event.