I’ve stand-up paddleboarded around Lady Bird Lake, navigating my way among the flotilla of other paddleboards, canoes, kayaks and dogs chasing balls.

No offense to those who love a mellow afternoon on flat water, but sometimes I need more action. That’s why I headed to San Marcos recently to try paddleboarding on moving water with certified instructor Karla Held.

“It’s a no-brainer,” Held said about her preference for paddling in rivers instead of lakes. “You’re doing less work because you’re going with the flow, literally, and you go faster. You’re challenged to read the water, and you need whitewater skills if you’re going into rapids.”

We convened in the free parking lot adjacent to the Lion’s Club Tube Rental facility at City Park in San Marcos. From there, we unloaded her inflatable boards, paddles, helmets and personal flotation devices, hauled them a hundred yards or so to a set of stone steps that led to the river, and prepared to launch.

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The San Marcos river runs clear and cold up here. We positioned our boards in the water, against the sidewalk, and eased aboard, keeping our centers of gravity low. For best results, don’t try to stand up immediately. Kneel on the board, with a hand on each side, rise slowly to all fours, then ease into an upright position, trying to stay balanced.

I spent 15 minutes getting comfortable on the board, then pushed out into the middle of the river. Don’t worry if you fall — splashing into the water is half the fun in Texas in the summertime.

Then we pointed downstream.

On our way to Rio Vista Falls, a 10-minute paddle away, we passed clumps of Texas wild rice undulating under the water’s surface like mermaid hair. Steer clear — it’s beautiful to look at but endangered and protected. If you paddle this stretch, you’ll also see fish and turtles.

We passed under a bridge, rounded a bend and arrived at a cement walkway that leads from the shore to a small, cypress-shaded island in the middle of the river. Go left, around the island, admiring the knotted roots of some magnificent cypress trees. In a few more minutes you’ll arrive at Rio Vista Falls, a three-tiered set of rapids.

That’s where the real fun begins.

Since I’m a beginner, we pulled our boards out and walked to a spot below the first of three small drops to do a little scouting.

The bottom section looked easiest, so we decided to start there. Held reminded me that if I didn’t feel stable, I could kneel on the board for the ride. I snapped a helmet in place (rocks are a danger) and snugged up my personal flotation device.

She demonstrated, bobbling a little but making it over the drop in an upright position.

I put my board in the water next, clambered aboard and struggled a little to stand up. The currents pulled me swiftly toward the drop, and I didn’t have much time to prepare. Somehow, though, I got through in a standing position, without falling.

I tried three times, falling on my second and third attempts.

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Held, who learned to paddle at summer camp in Wisconsin when she was 8 and later worked as a rafting guide, gave me some pointers. She’s been teaching kayaking for five years and paddleboarding for three and will lead guided kayak and stand-up paddleboard trips at Camp River View in Concan this summer.

One, get a board that’s made for the river. “Inflatable is best, because it’s made to bounce off rocks and doesn’t get dinged,” she said.

Two, take at least one class to familiarize yourself with basic paddle strokes — forward, backward, sweep, draw and brace — and body position.

For easy paddling, adopt a neutral stance, with your feet about midway down the board and your eyes looking forward. You’ll want a more aggressive “surf” stance for the rapids, with one foot slightly turned and your knees slightly bent.

“Think of your knees as shock absorbers,” she said.

Rapids, she says, are less intimidating on a paddleboard than in a kayak. If you feel wobbly standing on the board, just kneel on it.

“If you fall off, there’s less consequence,” she says. “Just hang onto your paddle and hold the board.”

If you do fall off, roll onto your back, point your feet downstream and keep them near the surface.

Want to try it yourself?

To avoid crowds, go early. Tubers hit the San Marcos River in force starting at about 10 a.m., but if you get to City Park by 8 a.m. you’ll have the place mostly to yourself.

The San Marcos River isn’t the only Texas river that makes a good stand-up paddleboarding destination. Try the Colorado River between Little Webberville and Big Webberville parks, the spring-fed Comal River in New Braunfels or the Upper Guadalupe River, between Bergheim Campground and Edge Falls Road. The Llano, Frio and Nueces rivers also offer possibilities.

And bring your sense of adventure.

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