Perhaps the shore secretly awaits the ocean's return, prays to the stars that the waves will not give up. She begs him to return because in that brief moment, he is able to wash away her past.
So many people walk all over her, taking what they like, disregarding what they don't, but when he comes back, she is left with a clean slate. Momentarily, she can forget her imperfections because he is all she knows.
And when he leaves, he leaves with an unspoken promise that he'll return.