Break, break, break, On thy cold gray stones, O Sea! (1-2)
The sound of the sea waves "breaking" is repetitive and meaningless, setting up the theme of the speaker's worry that his own crying and grief is equally repetitive and meaningless.
And I would that my tongue could utter The thoughts that arise in me. (3-4)
The speaker claims that he is unable to express his own thoughts, which seems odd, given that he goes on to finish one of the more famous poems in the English language. He phrases his inability rather passively: he doesn't say, "I can't utter what I'm thinking," but rather, says that his "tongue" can't "utter" it, as though his tongue were somehow separate from the rest of him.
O, well for the fisherman's boy, That he shouts with his sister at play!(5-6)
Here's that syllable "O" again – it's a meaningless sound, like the sound of the waves or the happy "shouts" of the "fisherman's boy." The fisherman's boy is not shouting words – at least, the words are not repeated by the speaker – he's just making noise, but without expressing anything. The speaker is worried that that's exactly what he's doing in this poem.
O, well for the sailor lad As he sings in his boat on the bay!(7-8)
Like the "fisherman's boy," the sailor makes noise, but without articulating any words (again, none that the speaker tells us about). And again, the speaker repeats that meaningless syllable "O" at the beginning of the line.
And the sound of a voice that is still!(12)
The speaker doesn't say <em>what</em> he wishes the voice was saying; he just wants to hear the "sound" of it. This poem is awfully full of inarticulate sounds – i.e., sounds that have no words or real meaning associated with them.