What are the motifs in A Drink of Water by Seamus Heaney?

Love is a recurring idea. In "A Drink of Water," the depicted love is familial, not amorous as in many other sonnets. Perhaps the best analogy is one that "A Drink of Water" implicitly draws: the poem as a toast. A toast is an act of love: one only toasts those of whom one feels fondly. Yet, if shared affection inspires a toast, it also requires a certain level of formality.