But as quickly as the lights of Florida came into view, police lights burst upon them. A siren wailed. People screamed, a helicopter circled overhead and an officer on a sheriff’s boat pointed a long gun toward them. Uniformed men climbed on board, yelled orders and handed out life jackets. The group of 54 people was transferred to a small Coast Guard cutter. As the sun rose over Florida just beyond them, a man with a tattoo on his arm of a hand making the sign of the benediction began recording a video on his phone. “As you can see, we are in Miami,” he said. “As you can see, we are on a boat with a bunch of small children.” He intended to send the video to relatives waiting for him on land, and he urged them to contact lawyers. But his phone was confiscated, and the video was never sent.

The Coast Guard frames its operations in the sea as lifesaving work: Crews rescue people from boats at risk of capsizing and pull them from the water. But the agency, which is an arm of the Department of Homeland Security, also operates as a maritime border patrol, its ships as floating holding facilities. Since the summer of 2021, the Coast Guard has detained more than 27,000 people, a number larger than in any similar period in nearly three decades. On a single day in January, the agency’s fleet of ships off the Florida coast collectively held more than 1,000 people. The public has no way of knowing what happens on board. Unlike at the U.S.-Mexico border, which is closely monitored by advocates, the courts and the press, immigration enforcement at sea takes place out of public view.

The Coast Guard routinely denies journalists’ requests to witness immigration patrols, but in early March, I learned that several days earlier, a boat carrying dozens of Haitians had been stopped so close to land that they were first chased down by the Palm Beach County sheriff’s marine unit. Among them were three unaccompanied children: two young sisters and a 10-year-old boy. In the months afterward, I obtained a trove of internal Coast Guard documents, including emails and a database of the agency’s immigration interdictions, and I tracked down Tcherry, Claire and Beana and 18 people traveling with them. Many of them told me about the five days they spent detained on Coast Guard ships — an experience, one man said, “that will remain a scar in each person’s mind.”

People intercepted at sea, even in U.S. waters, have fewer rights than those who come by land. “Asylum does not apply at sea,” a Coast Guard spokesman told me. Even people who are fleeing violence, rape and death, who on land would be likely to pass an initial asylum screening, are routinely sent back to the countries they’ve fled. To try to get through, people held on Coast Guard ships have occasionally taken to harming themselves — swallowing sharp objects, stabbing themselves with smuggled knives — in the hope that they’ll be rushed to emergency rooms on land where they can try to claim asylum.

The restrictions, combined with the nearly 30-year spike in maritime migration, created a crisis for the Coast Guard too, leading to what one senior Coast Guard official described in an internal email in February as “war-fighting levels of stress and fatigue.” Coast Guard crew members described to me their distress at having to reject desperate person after desperate person, but the worst part of the job, several said, was turning away the children who were traveling alone. From July 2021 to September 2023, the number of children without parents or guardians held by the Coast Guard spiked, a nearly tenfold increase over the prior two years. Most of them were Haitian. “The hardest ones for me are the unaccompanied minors,” one crew member told me. “They’re put on this boat to try to come to America, and they have no one.”