Here is the poem:
Break, Break, Break
Break, break, break,
On thy cold gray stones, O Sea!
And I would that my tongue could utter
The thoughts that arise in me.
O well for the fisherman's boy,
That he shouts with his sister at play!
O well for the sailor lad,
That he sings in his boat on the bay!
And the stately ships go on
To their haven under the hill:
But O for the touch of a vanish'd hand,
And the sound of a voice that is still!
Break, break, break,
At the foot of thy crags, O Sea!
But the tender grace of a day that is dead
Will never come back to me.
The poem was written to mourn the death of Tennyson's friend, Arthur Hallam. The poet is watching the waves break on the shore and he is grieving for his friend, whose hand he will never touch again, whose voice he will never hear again.
The poet is talking to the sea as if the sea were human, so this is an example of apostrophe.
"Haven under the hill" is a phor for ships disappearing in the haven of the harbor (under the hill).
Now, you try: what is "the tender grace of a day that is dead"? Why does the poet mention the fisherman's boy and the sailor lad? How does what they are doing contrast with the poet's mood? How does the strong meter add to the poem's impact? Is it an appropriate meter for a poem with such strong emotions?