We might understand this phrase to refer to fish and other sea creatures, in distinction from the creatures on the earth. That certainly would be accurate in the sense that sea creatures also join in praising the Lamb. Scripture, however, also pictures the sea as the habitat of devilish forces (Psalm 74:13–14; Isaiah 27:1). In this understanding, the beast that John later sees arising from the sea (Revelation 13:1) has already (grudgingly, no doubt) chimed in with every other creature in God’s world to acknowledge that “blessing and honor and glory and might” belong forever and ever
to him who sits on the throne and to the Lamb.
13 And I heard every creature in heaven and on earth and under the earth and in the sea, and all that is in them, saying, “To him who sits on the throne and to the Lamb be blessing and honor and glory and might forever and ever!”