We were crossing the lake the other day, the old boat doing its thing, when my daughter asked a question from the back seat.

"Dad, why do we wave at people in other boats but not at people in cars?"

I slowed down a little. I didn't have an answer ready.

You know the wave. Another boat comes toward you, close enough to make out the people in it, and a hand goes up. Sometimes it's the full arm. Sometimes just fingers lifted off the wheel. You don't know them. You'll probably never see them again. You wave anyway.

Everybody does it. Nobody taught us. It's a rule of the lake that was never written down, older than anyone who follows it.

Try it on the 400 and see how far you get.

The road is a different country. Signs, signals, brake lights, everyone sealed in their own glass and steel, racing to be somewhere else. Nobody's looking at anybody. There's no room out there for a raised hand.

The water runs slower. The engine hums along, the light moves on the waves, a loon goes down and you wait to see where it comes up. You have time to notice the other boat. The people in it. The fact that they picked the same stretch of water, the same afternoon, as you.

On the road, we’re in our own bubbles, zoned out, or racing to get somewhere. It’s a noisy, hectic space, not exactly a breeding ground for those friendly waves we share on the lake.

Maybe that's the whole answer. I see you. We're both here. Neither of us is anywhere else.

And the people waving back learned it the same way my daughter is learning it now. From the seat of somebody's boat, watching a hand go up, understanding without being told that this is what we do here.

I was still working out how to say all that when another boat came around the point.

She beat me to it. Her hand was already up.