According to John’s record, the very next thing he saw, after mentioning the seven angels with the seven last plagues was “a sea of glass, mingled with fire” (Revelation 15:2). The text says that those who were victorious over the beast, his image and the number of his name were able to stand upon the glassy sea (thalassa – G2281), which was “mingled with fire” (Revelation 15:2).
My first thoughts about this scene take me back to Jesus when he walked on the Sea (G2281) of Galilee or Tiberius (John 6:1, 16-19). Speaking of the same incident, Matthew said, when Jesus walked out upon the sea to where his disciples were in the ship, they were afraid, supposing he was a spirit (Matthew 14:25-26). So, when he identified himself, Peter asked him to call him out that he may walk out to him. When Jesus called him, Peter also began walking on the sea (Matthew 14:27-29). However, when he considered the strong wind, and probably the great waves, Peter lost faith and began to sink and had to call out to Jesus to save him (Matthew 14:30-31).
What we have in John 6 and Matthew 14 is a picture of a stormy sea, a mighty sea stirred up by the strong winds. However, when we come to Revelation 15:2 we have a calm, very peaceful scene—a glassy sea. In Revelation 4:6 it is so clear that it is compared to crystal, and this same sea (G2281) is before the throne of God. Yet, as calm and as peaceful as this scene appears, the text does say fire is mingled with its waters. In other words, the faith of those who had overcome in the Apocalypse was tried, just as Peter’s faith was tried by what he saw in the mighty and dangerous winds and waves of the Sea of Galilee. While Peter began to sink, because he considered the troubled waters, these in Revelation 15:2 stood upon the sea, because their faith in the blood of Jesus (cf. Revelation 12:11) had made the sea calm under their feet.
The idea that the same sea could be troubled or calm in accordance with one’s faith in Jesus causes me to wonder. Could this calm, glassy sea (thalassa – G2281) that is mingled with fire have any relationship to the lake (limne – G3041) of fire, burning with brimstone that is mentioned later in the Apocalypse (Revelation 19:20; cf. 20:10, 14-15; 21:8)? At first one might think two different bodies of water are mentioned, because one is called a sea (G2281) and the other a lake (G3041), but this is not a good argument, because, although Matthew, Mark and John use thalassa (G2281) to describe the Sea of Galilee (John 6:1; Matthew 4:18; Mark 1:16), Luke always uses limne (G3041) to describe the same body of water (Luke 5:1-2; 8:22-23, 33).
Although Luke calls it the Lake of Gennesaret, clearly he is speaking of the same body of water as Matthew and Mark (cf. Matthew 14:18; Mark 1:16). All three land areas: Galilee, Tiberius and Gennesaret bordered what we commonly refer to as the Sea of Galilee, but it was called by all three names in the Gospel narratives. So, is the calm glassy sea that was mingled with fire (Revelation 15:2) the same as the lake of fire mentioned in Revelation 19, 20 and 21?
Those who were victorious over the beast, his image and the number of his name were able to stand upon the glassy sea that was mingled with fire. It is interesting that the Apocalypse tells us that those who had overcome were not hurt by what it calls the second death (Revelation 2:11:20:6). Moreover, the second death is the destruction of all who are not found in the “book of life” (Revelation 20:15), murders, idolaters, unbelievers etc. (Revelation 21:8), even death and the grave are destroyed (Revelation 20:14). So, in the context of Revelation 15:2, what is a calm glassy sea to believers, is a lake burning with fire and brimstone to unbelievers and such like them, just as the Red Sea was salvation to Israel but death Pharaoh’s armies (Exodus 14:16-31).