TEQUESTA, Fla. — Crews pushed the limits of an ever-expanding search zone Wednesday for two teens missing at sea and nearing the boundaries of human survival.

The Coast Guard’s relentless hunt for the 14-year-old fishermen, Perry Cohen and Austin Stephanos, persisted for a sixth day as questions grew over how long it could go. Decision-makers were juggling a mix of “art and science,” Chief Petty Officer Ryan Doss said, trying to balance the knowledge of how long people can survive adrift with the unknowns on whether the boys had flotation devices and drinking water and what their physical condition is.

Still, authorities insisted their search would continue throughout the day.

“There’s been a lot of rumors that the search has been suspended. I just want to refute that,” Capt. Mark Fedor said, speaking on the street where both boys live. “The search has not been suspended. It is still active and open.”

Fedor was part of a Coast Guard contingent that met with the boys’ families for an hour Wednesday afternoon. Afterward, he declined to elaborate on the search or to answer reporters’ questions, but even a day earlier he acknowledged that with each passing hour, the prospects were direr.

The saga of the two boys from Tequesta, Florida, began Friday. Their parents believed their fishing outing would take them to a local river and waterway, as was the rule in previous solo trips, not the deep waters of the Atlantic.