This verse has been referenced in a number of threads.
After checking my Interlinear, it is my view that the translation of this verse does not actually match the Greek text at all.
I would suggest that the following paraphrasing more closely matches the Greek text: -
Now I saw a renewed/refreshed heaven and a renewed/refreshed earth/land, for the first heaven and the first earth/land had passed/moved away. Also, there was no more sea.
But I am sure that there will be other members that will want to justify the verse as it has been translated in the various translations: -
Then I saw “a new heaven and a new earth,” for the first heaven and the first earth had passed away, and there was no longer any sea.
Then I saw a new heaven and a new earth, for the old heaven and the old earth had disappeared. And the sea was also gone.
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.
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.
And I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea is no more.
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.
Now I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. Also there was no more sea.
Then 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.
Then 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; for the first heaven and the first earth passed away, and there is no longer any sea.
Then 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.
Then I saw a new heaven and a new earth; for the first heaven and the first earth had passed away (vanished), and there is no longer any sea.
Simply just believing our favourite translations without verifying the translation's contextual accuracy is always fraught with problems in our understanding of the texts.