When Bob and Beverly Vunesky came from California to Colorado at the end of May to begin their tour of the state’s colorful national parks, they knew to expect the unexpected.

But the Great Sand Dunes National Park and Preserve completely caught them off guard.

North America’s highest dunes were magnificent, swirling and swooping beyond the sage fields of the San Luis Valley, like a beige mirage out there against the verdant forest and frosty Sangre de Cristo Mountains.

“We just came for the dunes,” Bob Vunesky said. “But we didn’t know there was a river to cross. Insane!”

He and his wife joined crowds over the weekend to find Medano Creek raging through the dunefield — a phenomenon born from this year’s mighty runoff. The snowpack was 160% of average late last week up on Medano Pass, where snow still clings, soon to melt and create the creek’s ultimate surge.

The park’s geologist, Andrew Valdez, has charts showing this season to be just the fourth of its kind since 1995. The water was last this high in 2015, but historically the flow turns this lively every seven or eight years, Valdez said.

From a dormant year of drought, the cold channel has reawakened at the foot of the dunes, sending children on floats downstream, the waves crashing near their parents’ knees.

The true sea has emerged here where early settlers knew to be “a sea of sand as restless as the ocean,” a reporter wrote in 1898. In a disbelieving 1922 article, a member of the U.S. Forest Service confirmed the water’s existence, saying it should be “add(ed) to the list of Colorado’s great natural wonders.”

“The water is just one of those sights that can’t be missed,” ranger Eric Valencia now tells inquiring callers.

And so Ashley Lohman of Colorado Springs wasn’t going to miss it. The scene was reminiscent of her Florida days: people wading, building sand castles, catching rays beside coolers.

But this was different, unlike anything else. “A different world,” Lohman said from her beach chair, feet in the sand, eyes on those monoliths formed by wind and time. And yes, water.

Medano Creek is the lifeblood of the dunes, the deliverance of sediment from the mountains. In this compressed rift valley, the sand is trapped and built skyward by southwesterly and northeasterly winds — Mother Nature’s artistry.

“It looks like watercolor, like a painting,” Matt Dozier observed during his visit from Fountain.

He wanted to bring his kids to the water last year, but Mother Nature didn’t deliver. And amid climate change, it’s a wonder how often or not Medano will appear for future generations.

“It’s so hard to tell with the variability,” Valdez said, citing the area’s precipitation charts swinging between 5 and 21 inches in recent years.

From last year’s dryness came this year’s bounty, which meant the Vuneskys revising their Colorado travel plans.

“We couldn’t get over the northern passes due to the snow,” Bob said. “But here, I guess the water’s just fine.”