Pebbles by Margaret Atwood from her essays - Some objects of Wood and Stone.
This poem speaks to me in a way that I can almost imagine walking along the beach listening to the rhythm of the sea in the rhythm of the words. I have tried to find a link to a web page with the poem on but to no avail so, imagine the ebb and flow of the waves and then that is the rhythm I can hear. I found it in a copy of Shorelines- A collection of poems selected by Janie Hextall and Barbara McNaught.
The book is full of evocative, funny, sensitive and joyful poems all about pebbles, the sea and the coast.