Why does the new earth in Revelation 21 have no sea?
The new earth has no sea so that its entire immense surface is habitable, providing room for the billions upon billions of people in eternity. Removing the oceans ensures sufficient space for God's harvest of infants and aborted children who enter His eternal state.
Les explains that the new heaven and new earth replace the first, and there is no more sea. The reason is that there will be billions upon billions of people in eternity. Though Christianity may seem small, infants who die in infancy are God's harvest, and multitudes of infants die, including aborted little ones. So many will be brought into God's eternal state. The new earth will be so huge it will make Jupiter look like a playground marble, and because there is no ocean, every bit of it will be habitable. There will be so much room, plus members of the Body of Christ will rule and reign across the heavens.
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.