What has not changed over the years? Does this suggest something to you?

The sea has not changed much over the years. The sea is the only constant in all these years. All the other things have changed. The poet’s mother was so charming, lively and young back then. Now she is no more. Neither is the sound of her laughter.

This suggests that only something as large as the sea doesn’t change much over time. Other than that everything changes. People perish and life comes to an end.