I don't recall making sandcastles as a child, only making them with my children. My wife might insist that this is a slight distinction, that when I am scooping up handfuls of the moist, crushed-shell sand for the walls, or crouching beside my children and showing them how to gently pat-pat-pat the wide rectangular base from atop which our inner keep will dominate its small horizon, I am again a child, or perhaps for the first time a child.

She has taken pictures over these dozen or so summers since we brought our first child cross country from the Kansas heartland to the shores of North Carolina. Were we to arrange them side by side, these photographs might chronicle the building of a single castle, our work never done. The ocean draws closer in some; the wind whisks away the tops of parapets in others; a toddler sits unceremoniously on an outer wall in still another.

Recently I realized that I have been more prone to build castles when I have been hope-filled. With Caroline, my first and only daughter, before I knew how easily life itself can be taken away, I laboured in that sand for hours, my shoulders and back turning red as blood, my legs and arms and belly caked with grit. I built a foundation and she, two years old, helped me make it solid, chanting "pat-pat-pat" the way I'd taught her, because this is the best way to describe the gentle firming touch of our palms against this tenuously clinging material.

Caroline and I built walls within walls and towers atop the walls, and she called it a "cansackle," which is still the word that first comes to mind whenever I see these creations crafted with equal measures of whimsy and vanity. When we had built it as best we could, I held her against the wind sweeping in from the ocean, and was overcome with the knowledge that I would never be happier, and then a year later she was dead. After that, there were no sandcastles for a time.

Our second child, Caleb, came four months after the death of our first, and so he became at once a second and first child, ignored and attended as our grief demanded. Eventually we took him to those same shores. Reluctantly at first, but then with increasing abandon, I knelt beside him in the sand, on the same stretch of beach where I'd knelt with his sister—he the same age as she had been—and showed him how to shovel wet sand into his frail plastic bucket, then dump it in a pile and shape it into something like a rectangle with his small, eager hands.

Three brothers followed Caleb. Four boys trailing the girl who is gone, as if God were making some point of it all, perhaps that what departs is gone, or perhaps that neither our suffering nor our blessings are what we might choose. Four boys we love more than life, even to the point of staying married when we have wanted divorce, when the only path from pain seems to be two paths running in opposite directions.

I've had no heart for building sandcastles when my thoughts are consumed with what will come after, with whether this will be the last summer in which there will be one camera capturing our fleeting days on the sand, one house in which we sleep, one hand-holding goodbye to the ocean at the end of our visit, our faces turned out to sea, to the shimmering horizon of blue and green curving beneath the weight of its sky.

In these no-heart days, I half-heartedly pile sand with the littler ones and show them how to pack the plastic molds from which will drop already-crumbling towers or parapets. We build parts of castles, my sons' muted passion for the enterprise reflecting my own. Mostly we float in the swelling waves, or wander along the beach looking for whole shells amidst all the shattered ones.

At the end of every summer I pray we make it to another, all of us together, and so far we have. I am dreaming now of the castle we will build next time, of its walls reaching up to the knees of our youngest, of its moat to shunt away the in-rushing sea, of its towers upon towers and flags at its corners and all of us labouring at our portion, pat-pat-patting it into cohesion against the forces that pull all things apart where they can, where the walls cannot hold.

The last good castle we built had a round-domed cathedral at its center, and pressed into the very top of it a cross made of two small pieces of driftwood knotted together by dried grass. We left our castle at dusk, knowing it would all be washed away, that in the morning we would find only mounded sand, like a forgotten grave.

But in the morning our tiny cathedral remained, its cross bent by the wind but not taken, its rounded walls eaten but not caved inward. I tried to turn this into a lesson, but could find no words that would do anything but lessen what we felt in our hearts upon seeing it. Even now I cannot find the words, except to whisper that this is us, this cross-bearing cathedral in sand, this is us still here when by now we should have fallen, this is us still holding, still holding, by the grace of God, still holding.