Over the years, Sarah suspects, Tommy has floated to the surface of her.  They are swimmers now, far apart, on the top of the sea.

What does this mean?

At one time, Tommy was below the surface of the sea of Sarah, but over the years, he floated to the surface of the person Sarah.

At one time, neither Tommy nor Sarah were swimmers but now they are both swimmers on the surface of the sea of Sarah and they did not swim in the same direction and therefore are now far apart.

This is strange way to say they have grown apart and are getting further apart because they continue to move in different directions in their lives.

There was a time when they were together below the surface of the sea of love but they could not breathe there.  The sea turned from love to alchohol and prohibited sexual endulgence to salve the pain of living in a marriage that was no longer satisfying.  Indulgence is the cure for despair, it is yet another path to hurt and unhappiness.  Moving up and away from one’s own unhappinesss is not the right direction, it is just another direction.  Happiness is in the spot where you are, even if it is below the surface and alone, which is where you and I will all end up anyway.