O, well for the sailor ladAs 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 what 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.