The anticipated ecstasy of hymns, the crystal sea pictures the absolute, transparent holiness of God. Solomon was commissioned to reflect the pattern in the sea of his temple, provided for the cleansing of the priesthood. In this solid sea of glass, washing from sin and defilement is eternally out of the question. Nothing that defiles can enter into the dwelling place of God. Access to God's Heaven has as it's requirement holiness. It is a condition of entry and not a consequence. Absolute purity, the kind of righteousness that only Jesus Christ can provide, purchased by His blood and freely given to those willing to receive salvation by faith alone.
This crystal sea marks the boundary conditions of heaven. It is both heaven's floor and earth's ceiling. It is the extent of man's experience of the Divine when sought without Christ; a barrier of solid holiness.
Revelation chapter 5 paints a picture of the character and nature of the God of heaven:
Lion like in His Sovereignty
Calf like in His salvation
Man like in His incarnation
Eagle like in the transcendence of His Spirit
Get a glimpse of Glory
Get a glimpse of God
From a series of messages presented at Faskally House Family Week 2022 by Dr J Stewart Gillespie on the theme:
"Tell me There's a Heaven"