Titus Ogilvie-Laing was driving through the Queens-Midtown Tunnel last month in his beekeeping company’s van when he spotted something alarming. A stream of water was blasting out of the ceiling and pouring onto the enclosed roadway.

His mind flashed to a video he’d seen not long before: Dozens of vehicles were trapped in a flooded tunnel in China, with no way out. It was the sort of viral horror story that sticks with you — a nightmare scenario that New Yorkers don’t like to contemplate — and it suddenly felt a little too close to home.

His co-worker in the passenger seat, Matthew Flood, a native New Yorker, used his phone to capture the underwater waterfall.

“That’s a lot of water,” Mr. Flood, 27, recalled thinking aloud. “There’s no way that’s normal.”

Mr. Ogilvie-Laing, 33, focused on getting through the tunnel and out from under the East River — a waterway he was separated from by an 84-year-old feat of engineering that he did not fully comprehend.

By the time the beekeepers descended into the tunnel that day, the workers who maintain it had already been trying for hours to figure out what had gone wrong. The answer, they would eventually discover, was an apparent mistake made high above the gushing water — one that revealed the fragility of New York City’s aging transportation network.

But from the scramble to solve the mystery and quickly repair the leak, a different sort of picture emerges: of the resilience of the city’s infrastructure and of the everyday ingenuity and expertise required to maintain it.