You know that heart-pounding feeling when thunderous, Class III rapids propel your kayak toward a vertical dropoff, and you realize that you should have aimed for a more navigable channel, and you desperately try to change direction but it’s far too late for such a maneuver, so you’re swept over the ledge at a crazy angle, and your boat tilts past the tipping point as you brace for chaos?

Let’s back up a bit before I continue describing my experience last week on the Scantic River, which flows more than 40 miles from Hampden, Mass., to the Connecticut River in Windsor, Conn.

I would be joining longtime kayaking pals Phil Warner of Hampden and Ian Frenkel of Old Saybrook on a 5-mile whitewater section through Somers and Enfield. The removal of a 26-foot dam this past summer has created a free-flowing stretch that not only improves paddling but also expands the spawning habitat for American shad, river herring, sea lamprey and eels, according to the U.S. Fish and Wildlife Service, which helped pay for the $4.5 million project.

Conservation groups have long advocated for the dam’s removal, including the Scantic River Watershed Association, for which Phil serves as a director.

Normally the river is too “bony” this time of year for kayaking, but last week’s torrential downpours created sporting, spring-like conditions, so off we went, launching behind The Kids Academy Daycare building in Somers.

Phil, Ian and I would be following the course of the annual Scantic Spring Splash canoe and kayak race, with one notable adjustment — we no longer would have to portage around the old Springborn Dam, a gut-bursting quarter-mile detour that involved lugging boats over Heart Attack Hill.

The long-abandoned dam, built by Shakers in 1840 and used initially to power a gristmill and later a sawmill, had slowly deteriorated, and authorities feared it eventually would collapse, causing catastrophic flooding. The work was the largest dam removal in Connecticut history.

Phil took the right channel through what now consists of a narrow, churning gap at the old dam site, while Ian and I veered left. Both routes feature steep plunges that serve as a challenging prelude to hairier, more turbulent sections downstream: Stockers, Chimney and Staircase rapids.

We barely had time to catch our breath before Stockers loomed, a roiling, 4-foot drop into a haystack of cascading water, surrounded by boulders and a sheer, menacing wall.

“Stay left!” Phil shouted, taking the lead.

I watched his plastic boat bounce through waves and then disappear.

Seconds later, I saw Phil’s head pop back up, and he spun the boat around to watch upstream. I gulped. Me next.

With a few tentative strokes, I edged forward as the current sucked me into the vortex.

Bam! I bounced off a partially submerged boulder but managed to stay upright, and then, with an involuntary whoop, dropped near-vertically nose first into a giant, standing wave, where the sheer force of rushing water squirted my boat out like a watermelon seed.

Still upright. So far so good. One more pivot: I dug my left paddle into a low brace, veered out of the froth, and, finally, grinning ear-to-ear, pulled up alongside Phil.

“Piece of cake!” I lied.

Ian next made it through Stockers elegantly, and our giddy group raced ahead to the next hurdle: Chimney Rapids.

Whatever confidence I had built up by successfully navigating Stockers instantly evaporated at Chimney when I watched Ian, ahead of me, snag on a log and pin sideways. By furiously rocking his boat and shoving with his paddle, Ian was able to push free but then got swept around backwards amid swirling waves.

With flailing strokes, Ian turned his kayak forward, and he shot through the last few yards of rapids.

“Oh, man,” I told myself. “I can’t let that happen to me.”

A nanosecond later, I found myself snagged on the exact same log, trapped for what seemed like an eternity before I, too, spun around backwards and, with a gasp, completed a haphazard passage through the Chimney.

Phil, who had escaped unscathed, was exultant.

“This is great!” he gushed.

Next up: Staircase, only a few hundred yards from the finish near the South Maple Street Bridge in the Hazardville section of Enfield. I should mention that this rapid brings back unhappy memories of a Scantic Splash race from a few years ago, when my cockpit filled up with so much water because of a loose-fitting spray skirt that I had to exit the boat and wade gracelessly across the finish line, much to the amusement of spectators on the bridge.

Last week was to be my redemption.

But no. After flipping over and unsuccessfully attempting an Eskimo roll, I bounced along upside down for a dozen yards or so (that’s why we wear helmets), and now my problem was not a loose spray skirt but a tight one.

While the water raged around me, I twisted my head above the surface, took a deep breath, let go of the paddle and applied all my energy into yanking the snug, neoprene covering free of the cockpit coaming.

Finally, it popped off, and I squirmed out of the boat.

Watching this drama unfold, Phil had paddled alongside.

“You OK?” he asked.

I nodded. “Only thing that hurts is my pride.”

Ian had retrieved my paddle and helped me dump water out of the flooded kayak, which we dragged to a floating mass of logs, duckweed and debris near the bank.

I crawled back aboard and paddled the last 50 yards under the bridge. At least there was no crowd of spectators this time.

“The score: Staircase Rapids 2, Steve Fagin O,” Ian quipped.