Then I heard every creature—in heaven, on earth, under the earth, in the sea, and all that is in them—singing:
Revelation 5:13 NET
“To the one seated on the throne and to the Lamb
be praise, honor, glory, and ruling power forever and ever!”
The fifth chapter of Revelation introduced a scroll with seven seals. This scroll was held by God, the one sitting on the throne. And a call went out for someone worthy to break the seals and open the scroll. Initially, no one was found worthy to open the scroll. But then the Lion of the tribe of Judah, a slain Lamb, was found to be worthy.
When the Lamb was announced, the four living creatures and the twenty-four elders surrounding the throne (Rev. 4:4-11) erupted in praise (Rev. 5:8-10). Then, a vast multitude of angels encircled the throne and added their voices to the praise (Rev. 5:11-12). Finally, John heard praise coming from every other creature in all of creation, singing the praises of the Lamb and the one who sat on the throne.
Every Creature in All of Creation
Who are these in this final group? They are described as every creature in heaven, on earth, under the earth, and in the sea. Under the earth would likely be a reference to Hades (Rev. 20:13-14), the place of the dead, imagined as underground. And the sea has a generally negative view in Revelation. The beast came up out of the sea (Rev 13:1). The sea gave up its dead for judgment (Rev. 20:13). And in the new creation, there is said to be no sea (Rev. 21:1).
So those praising God and the Lamb include both the living and the dead, the good and the bad—every creature. This mirrors what Paul said in Philippians 2:9-11, that every knee in heaven, on earth, and under the earth will bow and every tongue confess Jesus as Lord.
People then, as well as now, reject Jesus as Lord. Rather than worshipping the creator, they worship the creation (Rom. 1:18-23). But one day, after it is too late, they will bow and sing the praises of the one they rejected while on earth.