Revelation 21:1 says, "Then I saw a new heaven and a new earth; for the first heaven and the first earth had passed away, and the sea was no more." Why would there be no more sea?
This passage puzzled me for a long time, too. After all, most of us enjoy the sea -- boating, swimming, snorkeling, etc. The sea is beautiful, and majestic. It would be a shame if there were nothing to take its place in the new creation.
But in ancient Hebrew thought, the sea was a dangerous place. Among Israel's neighbors, Yam was the terrifying sea-god. Unlike their neighbors the Phoenicians (modern Lebanon), the Israelites were not especially fond of boats. The primeval waters of Genesis 1 are frightening and chaotic. During "de-creation" (the Flood), the primeval waters deluge the earth, although Noah's family is rescued. The Red Sea too is the scene of divine rescue, although the waters flood back once the Hebrews have crossed to dry land, killing the pursuing Egyptians. Joshua too crosses the water (near Jericho), a similar miracle preparing the way for the Israelites to enter the Promised Land.
Skye Jethani expressed it well: "The massive power and unpredictability of the sea is why ancient peoples saw it as a symbol of evil. The inhabitants of ancient Israel, who were not a seafaring people, viewed the ocean as a realm of chaos, destruction, and darkness. Rather than a delightful place for recreation, to them the sea was a dark abyss to be feared. In their literature, including the biblical narrative, the sea became a metaphor for the forces of evil and disorder that stood in opposition to their God of order and beauty" (With: Reimagining the Way you Relate to God, 136).
I also like the way Philip Graham Ryken put it: "The sea represents everything that chafes and frets under the dominion of God; everything that is out of our control. But there is nothing like that in the new heaven and the new earth. Everything there is under the orderly blessing of God" (in D. A. Carson and Jeff Robinson Sr., eds., Coming Home Essays on the New Heaven and New Earth, 125).
So when John tells us that there will be no more sea, God is assuring us that in the new world there will be no more evil, chaos, or danger. I imagine (speculate) there will be no shortage of beauty and majesty! If the ocean is no more, then something better will have taken its place.
Further thoughts (sent in by an American friend):
I have become convinced that the “sea” of Revelation represents the people of the lost world. (Revelation 17:15 pretty much says as much. See also Revelation 16:3-6). The “sea” is a good metaphor because it is an unstable and dangerous place. In contrast, the “land” of Revelation represents the people of God.
The “beast” of Revelation 13:2 comes out of the “sea,” meaning that this beast comes from the world. In Revelation 10:2-6 there is an angel who stands with one foot on the “land” and the other on the “sea,” meaning that he has authority over both the people of God and the people of the world.
Further evidence: the second beast comes out of the “land” (Revelation 13:11). When we get to Revelation 19:20 this beast is referred to as a “false prophet.” It makes sense that a beast who is influencing the people of the “land” (people of God) would be called a false prophet while the beast who was influencing the people of the “sea” (people of the world) would receive no such designation.
As for the beast himself: I have come to believe that the number of the beast, 666, is a reference to 1 Kings 10:14. In this passage 666 is the amount of gold that Solomon received annually. Any studied Jew would have recognized that Solomon was doing a number of things that God had said not to do (Deuteronomy 17:16-17). Therefore “666” would be a good metaphor for worldly wealth and for the love of same.
So back to Revelation; we find that the beast of greed for worldly wealth comes out of the people of the world. Then there arises a philosophy within God’s people that it is okay to lust after the greed of the world. This would be the second beast who is also a false prophet. He teaches salvation through wealth.
Jesus' death and resurrection dealt a mortal wound to greed -- or at least it should have been. The resurrection proves the relative worthlessness of seeking salvation from wealth. Nevertheless, greed survived and flourished among both the people of the world and among God’s people until God throws greed into the lake of fire.