The vocative "my daughter" in "Marina" is, in my opinion, the speaker's ship or boat. It is rather difficult to tell, but the poem suggests that the speaker is a sailor in all aspects of the word. He has found himself in another marina, and he is unable to make a distinction between this and the many other marinas he has been to. Here, he asks:
What seas what shores what grey rocks and what islands
What water lapping the bow
And scent of pine and the woodthrush singing through the fog
What images return
O my daughter.
The use of "what" is not necessarily illustrative of this "unknown"place. Rather, the attitude of the stanza is one of indistinct elements. There are "grey rocks" and water is "lapping the bow." This is a similar image wherever the sailor goes. He can't distinguish between one marina and the next.
To take this idea further, he knows his boat very well. He knows the exact details of it:
Bowsprit cracked with ice and paint cracked with heat.
I made this, I have forgotten
The rigging weak and the canvas rotten
Between one June and another September.
Made this unknowing, half conscious, unknown, my own.
The garboard strake leaks, the seams need caulking.
This form, this face, this life
Living to live in a world of time beyond me; let me
Resign my life for this life, my speech for that unspoken,
The awakened, lips parted, the hope, the new ships.
He describes his boat exactly as he sees it. It is very distinct to him. In this way, it seems that he's taking "his daughter" whom he knows very well, on voyages the world round.