Summary: The millennium now being over, John is now introduced to a new universal order, the eternal state, where there are drastic changes in the cosmos as well as the marine environment.
John tells us in Revelation 21:1 (quickview) : "And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea." The millennium now being over, John is now introduced to a new universal order, the eternal state, where there are drastic changes in the cosmos as well as the marine environment.
The "day of God" will usher in the new heaven and the new earth (2 Pet. 3:12). Some scholars believe that the present earth and heaven will be renovated, while others argue strongly for the annihilation of the old order. Others note that the language employed is indefinite. They relate the new order in terms of a new relationship between God and His people. Yet many Old Testament passages stress the earth’s continuance. Ecclesiastes 1:4 (quickview)  states: "One generation passeth away, and another generation cometh: but the earth abideth for ever." Psalm 104:5 (quickview)  relates: "Who laid the foundations of the earth, that it should not be removed for ever." Psalm 119:90 (quickview)  declares: "Thy faithfulness is unto all generations: thou hast established the earth, and it abideth." According to Vine, the word new (Kainos), means "not new in time, recent, but new as to form or quality, of different nature from what is contrasted as old." Paul had a similar thought when he stated: "Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new" (2 Cor. 5:17). Swete notes that "it suggests fresh life rising from the decay and wreck of the old world." Alford also states that "the vision does not necessarily suppose the annihilation of the old creation, but only its passing away as to its outward and recognizable form, and renewal to a fresh and more glorious one."
There will be topographical changes: "there was no more sea" (Rev. 21:l). Whereas three-quarters of the earth is now covered by seas and oceans, the eternal state will find a reversal of these conditions. To the ancient mariner the sea symbolized the unknown, a sense of mystery. The Psalmist declared: "Thy way is in the sea, and thy path in the great waters, and thy footsteps are not known" (Psa. 77:19). For the Apostle John the sea meant separation from his friends. In the new order there will be no more mystery, no more separation. "For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know even as also I am known" (1 Cor. 13:12).
Next John sees the "holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband" (Rev. 21:2). The new Jerusalem has ever been the hope and anticipation of the saints of both the Old and New Testament. We are told that Abraham "looked for a city which hath foundations, whose builder and maker is God" (Heb. 11:10). The OT saints are described as desiring "a better country, that is, an heavenly: wherefore God is not ashamed to be called their God: for he hath prepared them a city" (Heb. 11:16). Jesus had spoken to His disciples in the NT concerning its preparation (John 14:1-3 (quickview) ). The Hebrew believers were told: "But ye are come unto mount Sion, and unto the city of the living God, the heavenly Jerusalem" (Heb. 12:22). They were also informed that "here have we no continuing city, but we seek one to come" (Heb. 13:14). Paul speaking to the Galatians stated: "but Jerusalem which is above is free, which is the mother of us all" (Gal. 4:26). The new Jerusalem is also mentioned in relation to the believer’s in the church at Philadelphia (Rev. 3:12). John will later be taken to a high mountain where he will be given a vivid description of the heavenly city (21:9-10)