The complex has its own pool, just for the houses inside the gate. Full-time lifeguard, a shallow kids' pool, and a deep adults' pool next to it. We arrived in the first days after they'd refilled and treated it for the season, which meant the water was cold enough to make a five-year-old reconsider her life choices.

The girls had been getting ready for this for months. Back home in Toronto they've been working with their swim teacher, building up confidence in their floaties, the kind that strap on across the back, not water wings. Each week, slightly less foam, slightly more kid. By the time we left, Nora could push off and cover a short distance without the floaty at all. She had momentum.

Then she put a toe in the water.

For the next few days, Nora wasn't getting in. Too cold, too unfamiliar, too far from the version of the pool she'd been beating in Toronto. Maeve, two years younger and operating on a completely different threat-assessment model, strapped on her floaty and jumped. Within a couple of days she was doggy paddling from one side to the other, chasing us around, fully self-sufficient and loving the independence of nobody holding her up.

Nora watched from the deck.

What finally pulled her in wasn't us. It wasn't more coaxing or another demonstration of how the floaty works. It was a Swedish family who showed up later in the trip with a little girl who was already confident in the water. Peer pressure, applied in exactly the right dose at exactly the right moment. Within an afternoon Nora was in. By the next day she and Maeve were jumping in and out of the adults' pool together with their floaties, inventing games, ignoring us.

We got to sit on the edge instead of standing waist-deep next to them. Eagle-eyed, but on the side. That's the upgrade.

This is the thing I keep noticing with both girls. Swim class is where they pick up the fundamentals: kicking, breathing, getting comfortable with their face in the water. But it's other kids that get them to take the bigger risks. Sister, cousin, Uncle Dave, a girl from Sweden, doesn't really matter who. The push past the edge of "I think I can do this" tends to come from wanting to play, not from being taught.

And they're two completely different kids approaching the same pool. Nora is observational, runs the risk calculation, weighs the cold and the depth and what could go wrong before she commits. Maeve goes head-first, sometimes literally, which means she also goes under the water more, comes up sputtering, has a quick cry, and jumps back in. Different inputs, same result. Both get there.