In Huayen related documents I see the phrase "ocean samadhi" a lot. (also ocean mirror samadhi, ocea seal samadhi) Here is one source:
Huayan teaching features a range of holographic samadhi instructions drawn from the Flower Ornament Sutra. These practices help clear away limited preconceptions, foster fresh perspectives on reality, and expand mental capacities by expressing our deep interconnectedness.
... Another model is the "ocean mirror" or "ocean seal" samadhi. In this image, awareness is like the vast ocean surface, reflecting and confirming in detail all phenomena of the entire universe. Waves of phenomena may arise on the surface of the ocean, distorting its ability to mirror plainly. But when the waves subside as the water calms and clears, the ocean mirror again reflects all clearly. Our individual minds are like this, often disturbed by turbulence, but also capable of settling serenely to reflect clear awareness.
I searched Cleary's Avatamasaka translation and only found the word Ocean used as a metaphor or simile. (The kindle stops searching at 500 hits, well before the end of the book)
Anyhow, can't tell if this is a sort of visualization exercise, literally involving thinking about waves and the ocean, or if this is just a metaphor for the meditative states achieved in samyak-sam-bodhi.