I am slow to panic. This seems useful in the moment when my child’s head is slipping under water and I can’t reach him and he can’t swim. Less so hours later as I lie in the dark and see that picture of him going under, over and over again. In the middle of the night, where everything that I approach with equanimity during daylight hours comes back to haunt me, a measure of panic finally comes.

We spent an afternoon last week at a waterfall on the Maitland River. Was it a shallow waterfall, or is it easier to picture as a set of rapids? It was our first time at this spot, although my husband remembers a distant childhood visit with his parents. We meet friends, picnic, climb down to the river, and walk in.

At the top of the falls, the water is shallow, the rocks bare in spots, then there is a series of descents, like steps, to the deeper water below. Children are playing in the falls, some confident swimmers jumping in from above, one girl fishing from the top, a mother sitting in an old-style lawn-chair above the falls, reading.

At the very base of the waterfall the water is deep, but further away from it, there are random pockets of deep and shallow, perfectly round holes carved out in the rock to sink into, stones jutting up at the next step to raise you up. Surreal tricks of depth, so that in spots a child can stand knee-deep beside his father, who is up to his chest.

In retrospect, I realize that I didn’t have a full understanding of the hazards, my first time here. Of the places on top where shallow water drops between the deeply carved rocks into a powerful current. Of the places at the bottom where the secure ledge to the sides of the waterfall plunges down into blackness.

My older son can swim, enough to keep his head above water – which is what he prefers – as he tests the gentle current that draws him away from the falls, over and over again. I see the tip of his face sticking up, smiling to himself, as he drifts and then swims back against the current so he can drift again. I keep an eye on him.

My younger son can’t swim yet, despite lessons and lots of opportunities to practice. We play catch with his body through the water, letting the current glide him a short distance from one adult to another, letting him practice kicking briefly in the moment before he is in someone’s arms again.

But then he follows his friend up to the top of the falls, where other children are walking. It’s shallow up there, I think; he needs some room to explore.

I turn to my other son, turn to my friends, let my attention move away briefly. Immersed in the experience.

Then a sudden urgency makes me look up and scan the scene. Where is he? He’s not at the top of the falls; he’s not on the shallow ledge; I can’t see him anywhere. I find him with my eyes in the instant he steps confidently forward from the ledge into the deep water. I see his moment of confusion at not finding his footing, then his head slipping under, struggling to stay above. He slips seamlessly. He doesn’t make a sound.

There is a pause in everything. Then I yell out to him, I yell to my husband who is closer. It all seems to take a long time, and I am pushing against the current to swim towards him.

In that moment, a stranger who is swimming beside my son – but with his attention focused on a child of his own – hears our calls, reaches out his arm and grabs my child out of the water. We reach him and he has hardly submerged. I tell him he’s okay, everything’s fine, we’ve got him; moments later he is back to laughing and playing with his friends.

I walk with him around the shallow sections; I instruct him to look down often; I point out the darkness where the water is deep. I tell him that he must stay close to us for now. Everything I should have done right from the start. We work on treading water.

We find a place where we can sit with water falling against our backs, shallow water warmed by the sun massaging our spines as it falls. We sit side by side, all of us, reveling in how good this feels.

My older son climbs around the side of the falls, up to the bare rocks at the top, where incongruously someone has placed a picnic table. He climbs up on the table, and twists his legs into a lotus position, closes his eyes briefly, clearly pleased at this picture of himself. I smile to him. He gets up and starts navigating the rocks to walk towards his friends, on the other side of the fall. He walks through the shallow water. I watch him.

Then he makes an error in judgment. He steps into a pool at the top of the fall, a shortcut. The force of the water catches him. Now he is the one pulled under, head briefly submerged. My husband jumps up: “Oh God!” One of our friends jumps up at the top of the fall. I do not seem to be moving. Everything slows down again. But my son has grabbed the rocks, he is clinging to the side. He struggles to climb out of the deep pool and his younger friend comes towards him and drags him out over the rock.

My husband goes to meet him. I see him talking sternly, and I wince a little. Then a short while later, he is comforting our son.  Eventually, I am with my son. He is scared, upset. There is a difference in the response of the ten-year-old to that of his younger brother. He lingers, replays the moment, sees the big picture. “I could have died,” he says.

I listen to his fear, but also try not let the story take hold. I tell him about a time when I was his age, at a cottage, where I suddenly got pulled under and someone dived to fish me out. I remember it clearly, the moment of panic.

I tell him that his instincts were good; that he reached out right away for the rock; that he would have caught himself if he had been swept further. I tell him we were watching; that we were close; that it was only a momentary scare. I try to believe all of this.

I walk around with him looking at the currents, talking about the force of the water, talking about how to respect that power, how not test it unnecessarily. We swim some more, sit in the sun, wade further downstream, exploring. My older son’s mood turns; he has accepted that everything is okay; he has decided that it was a great day, despite.

I talk to him about keeping your head above water; how real the metaphor is for me that day. About what it means not to panic, to get air whenever you can. I also talk about what it means to be in over your head. As sometimes it feels like I am, as a parent.

Later, I lie awake thinking about the mistakes I made, thinking about the thin edge between safety and danger, thinking about the turning points to a potentially wholly different future. About risk assessment. About what it means to learn from experience; how terrifying that can be.

I looked over at the right moment; another adult was within reach; the rock was there to grab; and so it was a beautiful day, full of adventure and resilience and learning.

But the fragility of my children is also present for me, the fragility of all children, the fragility of our lives as they are, the fragility of everything, and so I hold on tight that evening as they fall asleep.

A week later is the next time I’m in water with my kids, on a lake near my parents’ house. Within a few minutes of getting in the water, my younger son figures out how to swim. A very simple paddle, and not far, but over and over again he swims to me as I count how long he can keep himself above water.