After time and weather have eroded a vision to sand, its attendant body may be found standing with wet feet in the remains, facing the invisible tide. There is substance here, too, but no name. We pour our loaded attempts to define it into the sea and she absorbs them, one after another metaphor, including this one now, until it becomes possible to say that the one with their feet at the edge of a lapping wave is actually long gone, adrift––waving, or not, and we hold cupped hands above our eyes, saying back and forth, Look, look out there, squinting.
The sea is sure a mysterious something. Hard to describe but your poem did it justice.