Here’s how things go when your children are little: They are bored on a lazy summer afternoon, so you suggest water balloons. Suddenly you are up there on the level of Wonder Woman. Your children will follow you anywhere. You are a genius. Your offspring know no one on this Earth who is cooler than you. Inside, you think you are doing parenting better than anyone else in the neighborhood.

Then your children become teenagers.

Despite what the textbooks tell you, it is an abrupt shift. Sometimes even, it feels like over night. One of my sons had cracks in his voice in February, and by March, I promise you, he had basically become a man. I texted my husband in mid- February and said, “He’s doing something really annoying with his voice, and it’s driving me crazy.”

Husband: “Maybe his voice is changing.”

Me: “No way! Not my little boy.”

Then, boom, he woke up and his childhood self was completely gone. So was my ability to amaze him.

Sometimes, I still see my older boys’ younger selves — especially in their eyes — but mostly, their faces have changed right along with their voices. And most devastating of all, I’m no longer Wonder Woman. Suggesting water balloons is likely to invite eye rolls.

Just a few short years ago, I logged uncountable hours paddling my kids around in a canoe in the summer. We walked around in the forests and looked for swimming holes. I was older and wiser, and I had all the ideas. I still felt like a young mom. I even referred to myself as a young mom in this column.

But this summer is … different. Maybe because I turned 40 this year, but more likely because my oldest boys are 14- and 16-years-old. Nothing makes you feel older than spending even just a little time with new teenagers. They reference things you don’t understand. They are less easily entertained. And most of the time, they have you on the sideline while they come up with the ideas.

This summer, I’ve spent dozens of hours as the spotter in a boat while my boys water ski. They are new skiiers, and while I watched from the safety of the boat, I yelled things like “Stay in a ball!” and “Let the boat pull you up!” like it hadn’t been almost 20 years since the last time I skied myself. I was an observer, no longer a participant, and that shift had not really occurred to me until my boys finally mastered skiing and one of them said, “Maybe you should try it, Mom.”

“Oh, no, no, no,” I said. “I just watch from the boat. I suggest water balloons, and I walk through forests and encourage you to swim in really safe pools of shallow water. But now I’m a sideline kind of mom, hanging out on the back of the boat and watching you live your lives.”

My boys stared at me.

One said, “You should never ask us to try something that you aren’t ready to try yourself.”

Another one reminded me that I’ve often said I want them to keep me young and active. “Skiing is active,” he said.

And so, the next thing I knew, I was staying in a ball in the freezing cold water, attached to the boat by a rope, and praying to God that I didn’t break a leg while water-skiing.

I didn’t get up the first time, and for a moment, I felt like I had done my duty. The boys could put that check in the box: Mom tried waterskiing. But then they said, “You’ll get it this next time,” and they threw me the rope again.

The boat lurched forward. I stayed in a ball and let it pull me up. And suddenly, I was skiing. I have not seen such excitement from my boys since the days when I suggested water balloons when they were toddlers.

I’d like to tell you that I looked really cool, but that would be a lie. I screamed the whole time, and I went over the wake bent over like I was holding onto a walker. I’m sure I looked ridiculous, and I’m certain I didn’t look skinny in my bathing suit. But I was out there participating with my boys in the things they enjoy now, and they were cheering from the back of the boat.

Which is all well and good, but do you know what happens to hamstrings when you ride on skis bent over like that? I now have new criteria for what makes a mom feel old: Waking up the next morning after waterskiing and walking to the restroom.