It's certainly an interesting opening line, as many of us only witness seaweed as if it is dumped at the beach, often our childhood Summer seaside family holidays. 'Beached' in itself might suggest marooned. As a lover of seaweed for breakfast, be it a Welsh one or a Japanese snack, the entity is home.
But now I'm of Agatha Christie mysteries, and of course:
"O what a tangled web we weave when first we practice to deceive."
Sir Walter Scott (Marmion 1808)
a periwinkle rotates
deeper into itself
3Lights: Promenade: haiku beside the seaside (2008) curator: Liam Wilkinson