DHAKA, Bangladesh — Its name translates into “floating island,” and for up to 100,000 desperate war refugees, the low-slung landmass is supposed to be home.

One refugee, Munazar Islam, initially thought it would be his. He and his family of four fled Myanmar in 2017 after the military there unleashed a campaign of murder and rape that the United Nations has called ethnic cleansing. After years in a refugee camp prone to fires and floods, he accepted an invitation from the government of neighboring Bangladesh to move to the island, Bhasan Char.

Mr. Islam’s relief was short lived. Jobs on the island were nonexistent. Police officers controlled the refugees’ movements and sometimes barred residents from mingling with neighbors, or children from playing together outside. The island was vulnerable to flooding and cyclones and, until relatively recently, would occasionally disappear underwater.

So, in August, Mr. Islam paid human smugglers about $400 to ferry his family somewhere else.

“When I got the chance, I paid and left,” said Mr. Islam, who asked that his location not be revealed because leaving Bhasan Char is illegal. “I died every day on that island, and I didn’t want to be stuck there.”

Myanmar.