Ashtavakra Gita

As the ocean is not other than its waves, so the enlightened man is not other than the world he sees

Uses the ocean-and-waves image to explain how a realized person can remain non-dual while still perceiving a world full of separate, changing things.

The ocean-wave analogy is one of the most frequently borrowed images in non-dual literature, and chapter 11 puts it to specific use: a wave is never a substance different from the ocean, only a temporary shape the ocean takes, so no contradiction exists between the ocean's unity and the multiplicity of its waves. Applied to the enlightened person, the teaching says the world of distinct objects a realized person perceives is not separate from, or a threat to, the non-dual self — it is simply the self's own appearing, the way waves are simply the ocean's own moving. This addresses a natural objection to radical non-dualism: if only the self is real, how does the enlightened person still see a world of many things? The answer given here is that seeing multiplicity was never inconsistent with being one — only believing the multiplicity to be independently real was the error.

Ashtavakra Gita