The poem is that the poet is unhappy that the belief in a supernatural world's existence is reducing. He represents this by the "sea of faith", saying that it is withdrawing like the ebbing tide, the specific context being a honeymoon poem written around 1851 not long after Frances Lucy Wightman married Arnold Wightman showing the "sweetness and light" that Arnold found in classical content which he based his view on the English culture from.
