Almost any item can be given symbolic significance. The blessing stones or shells ritual is perfect for a natural setting : the exchanging of stones or shells by the bride and groom, coloured or inscribed, instead of, or as well as, rings. The stones are cast by the newly-weds into the sea or a river to symbolise their unity during the ebb and flow of their lives together.
Something like this can be said: “… these stones are as old as the earth and as enduring as love…the stones will endure the tides of the ocean just as your love will endure the tides of life…in the depths of the ocean lie the secrets and dreams and promises of your marriage… please cast your stones into the water.”
A variation on this is to provide a bowl of coloured stones for guests to take. The guests are invited to write a wish on a card, read it out and cast their stones into the water. Even, in fact, a bowl of water, which can be taken home as a keepsake.
The same can be done with shells at a beach wedding. This anonymous reading is ideal:
“As the sea is eternal, so is our love;
as the wind is all-encompassing, so is our love;
as the earth is solid beneath our feet, so is our love.
And yet our love is so great
That it even soars above the sea and the wind and the earth.”