Walkers on a beach at low tide search the exposed peat for traces of a forest that the sea swallowed long ago. The ancient stumps are now home to bladderwrack, so land and sea seem to have swapped places. The speaker and their companion share a small, childlike thrill at finding scraps of root-bark, and that simple excitement sits beside something more unsettling, like the gull's cry turning "eldritch."
The seaside town adds a modern layer. Its ice-cream colors look cheerful against the Atlantic, yet the high street is "already lower than the beach," a quiet warning about rising water. The mention of Tisha B'Av, with families strolling the sea wall, suggests a day of mourning set against an ordinary holiday scene. The mood is curious and tender, with dread underneath. The closing lines, "land marks us / sea levels us," treat time and water as things that shape and equalize everyone, and the final "hello and goodbye" holds arrival and loss together.