The unnamed speaker of "Break, Break, Break" is sad. He also tells us that he can't express himself well. Grief has made him tongue-tied. And then he goes on for three more lyrical, lovely stanzas about how much he misses his dead friend. Who says he can't express himself well? Our speaker is too modest.
He is standing (or imagining that he is standing) by the ocean, perhaps in a port, watching the waves break. He can see and hear the local fishermen's kids running around, and can hear a sailor singing. Ships are cruising by. Our speaker can see and hear all of this, but he doesn't appreciate it – all he can think about is his absent friend. He might be observant, and maybe, if he weren't grieving, he'd be a nature lover. But as things are, all the beauties of the seaside are wasted on him. They just remind him of the way the earth keeps turning even after his friend has died.