The sea of glass surrounds the throne of God (Rev. 4:6). Two ideas are suggested in this description – transparency and peace. Transparency ideally is when one has no defects to hide. God is light and his presence reveals it. There are no hidden agendas. Glass also conveys the sense of calm. This is a reminder that there never is disturbance or agitation in heaven – it is the place of peace.
Some have suggested that the clearness is a reference to providence, that what is obscure to us and difficult to understand is straightforward and easy to grasp in heaven. Here we are getting some insight into his plans, but the full unfolding of his will takes place beside the crystal sea, where all is clear.
Another feature of the sea of glass was that it was mingled with fire. Fire is often a symbol of purity. It is certainly the case that heaven is the place of perfection. In Isaiah 6, we meet the seraphim, creatures who burn with holiness. The sinful world of planet earth is the opposite, indicated by seas marked by storms and dread and disasters. In contrast, heaven is the place of calm and consecration.
The residents of heaven are then mentioned. They are the ones who did not get involved in the activities organised by the beast and the image created by the second beast. They remained faithful whatever the cost and they reached the safety of the heavenly shore. All the dangers and problems connected to that are now behind them. We are told about them that they are prominent – I think that is the point of describing them as standing beside the sea. If we recall, earlier the dragon had stood beside the stormy sea of earth waiting to bring about the chaos that was organised by the two beasts. In contrast, the people of God are standing beside a better sea.
We should ask why people would stand beside a sea. After all, we don’t do so now. In olden times, everything came by sea. Trade, armies, politicians, and many other visitors. We could almost say that the sea brought the future to people because whatever it brought affected them for the rest of their lives. Whatever decisions were made across the sea eventually came to them. So we could say that the crowd standing by the glassy sea were waiting to see what the future would bring to them. Across the sea from them is God and he has great plans and prospects for them to experience eternally.