21:1And I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea.

And I saw a NEW HEAVEN and a NEW EARTH;

From the rest of this chapter's descriptions of the NEW JERUSALEM, we understand that this is "NEW" as in a "NEW" kind of HEAVEN and EARTH. This "NEW" HEAVEN and EARTH are not tainted by evil (2 Peter 3:8-13-13). The NEW HEAVEN and NEW EARTH may not even obey the current laws of physics. The theoretical physicist, Dirac, in 1928 proposed the existence of a positively charge particle, named positron, which was the opposite of a negatively charge electron. In 1932, Anderson experimentally observed the conversion of a photon into an electron and a positron pair. In 1955, an antiproton was produced in experiments with high-energy particles from accelerators. With these experiments which showed the existence of "antimatter", one could speculate all matter has an antimatter form, and that this antimatter if collected into a region in the universe could make up antimatter galaxies, for example. One should not go too much beyond this "antimatter" thinking, however, as verse 17 points out, we (and the angels) still are making measurements on a current human scale.

for the first heaven and the first earth passed away,

As Isaiah 24:1-5-6 shows us, this first heaven and first earth are polluted. They contained and were contaminated by evil. For this reason, the first heaven and first earth had to flee away from a pure, righteous God (Revelation 20:11).

and there is no longer ANY SEA.

The NEW EARTH will NOT have a SEA or place for evil to live. In an interesting extension, this implies that the NEW HEAVEN and NEW EARTH are not in our solar system. The Mars Rovers have proven that there is water on Mars, and water has been speculated for other moons orbiting other planets. One concludes then that the last two chapters of Revelation are almost entirely spiritual. However, since John SAW this NEW HEAVEN and NEW EARTH, it must have some physical dimensions (see verses 16, 18, and 21).

The sea is the first of the 7 things which will no longer exist. The other six are: death, mourning, weeping, pain (Revelation 21:4), the curse (Revelation 22:3) and night (Revelation 21:25; Revelation 22:5).

Often in our earlier discussions, we have pointed out that water is the container of spirits. If one adds in the blood, we find that these three, the Spirit and the water and the blood, bear witness to Jesus Christ (1 John 5:6-11) and His ability to give us eternal life (or access to this NEW HEAVEN and NEW EARTH). There are two kinds of water. There is Good Water (Revelation 22:1) and Evil Water (Revelation 12:10-17). Let's look at a few examples of the relationship between water and spirit(s):

Example of water and spirit relationship.
Kind of Water
References
At creation, the Spirit of God was moving over the surface of the waters. Heaven is formed in the expanse between the waters.
Good
Genesis 1:1-2,6-8
The flood was appropriate to harbor the spirits of the people who drowned.
Evil
Genesis 6:1-8, Genesis 8:13-19
Those who are anointed or chosen of God are protected from coming into contact with water.
   a) The chosen people leave Egypt through the Red Sea on dry land; pursuing Egyptians drown.
   b) The chosen people entering into the Promised Land crossing the Jordan River.
   c) Elijah and Elisha cross the parted Jordan River.
Evil

   a)  Exodus 14
   b) Joshua 3:14-17
   c) 2 Kings 2:1-14
Cast out demons request to go into pigs. The pigs subsequently rush down a steep bank into the sea. Sea now contains the cast out demons.
Evil
Mark 5:1-13-20
When an evil spirit leaves a man, it must find water to rest/reside.
Evil
Matthew 12:38-43-45
The dragon tries to drown the woman's child.
Evil
Revelation 12:10-17
The Sea Beast, one of the Unholy Trinity, comes up out of the Sea.
Evil
Revelation 13:1-10

This is not an exhaustive list where water is referred to in spiritual overtones. As you study the Word of God, you will find many references to water and its uses in judgment. You also will find good water put to use; although, those references are rarer.