Sea: Symbolical in John's Apocalyptic Vision
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Revelation 4:6
And before the throne was something like a sea of glass, as clear as crystal. In the center, around the throne, were four living creatures, covered with eyes in front and back.
Revelation 8:8, 9
Then the second angel sounded his trumpet, and something like a great mountain burning with fire was thrown into the sea. A third of the sea turned to blood, / a third of the living creatures in the sea died, and a third of the ships were destroyed.
Revelation 10:2, 5, 6, 8
He held in his hand a small scroll, which lay open. He placed his right foot on the sea and his left foot on the land. / Then the angel I had seen standing on the sea and on the land lifted up his right hand to heaven. / And he swore by Him who lives forever and ever, who created heaven and everything in it, the earth and everything in it, and the sea and everything in it: “There will be no more delay!
Revelation 13:1
Then I saw a beast with ten horns and seven heads rising out of the sea. There were ten royal crowns on its horns and blasphemous names on its heads.
Revelation 15:2
And I saw something like a sea of glass mixed with fire, beside which stood those who had conquered the beast and its image and the number of its name. They were holding harps from God,
Revelation 16:3
And the second angel poured out his bowl into the sea, and it turned to blood like that of the dead, and every living thing in the sea died.
Revelation 21:1
Then I saw a new heaven and a new earth, for the first heaven and earth had passed away, and the sea was no more.