Lyric discussion by satchito 

Cover art for Island lyrics by Coheed and Cambria

I agree that the island can be a metaphor of his comfort zone, or the way he had used to write music in the past, but the song also has a more literal meaning which is getting off the Island of Manhattan.

At the beginning you can hear the actual voice from the train (the 2 train going to Brooklyn, in other words, out of Manhattan). He says the fee is too big and the apartment is too small, something that anyone living in Manhattan (myself) can relate to. Of course that's just one reason, he can also be just overwhelmed by the small spaces, crowded streets, noise, and a long etc.

He also says that it was his choice so he clearly might have thought that living in Manhattan was a good choice but now he's regretting it.

Finally, if he's getting out of Manhattan intro Brooklyn, technically he wouldn't be "swiming back to shore" because Brooklyn is in Long Island, but that I take as a metaphor of going from a turbulent life to a more calm environment where he can actually rise a child with more confidence.

My two cents!

My Interpretation

@satchito That would be the Island of Long, as in, Long Island. :P (That's where Brooklyn's located.) In the New York area, many of us say we're going to, or that something is out on "the island" when we're going to Long Island.

Also, that would be the Q train. I should know, I live off that line, the 2 train does not use the same train cars, the R160 cars, which use the female announcer voice that can be heard in the song. The 2 train uses the R142, which is the male announcer.