The deceased was identified as Sundar Biswas, 55, son of Prafulla Biswas of Laudoba village in Dacope upazila of Khulna.
The boat, carrying 70 passengers, including women and children, sank in the river around 8am after it crashed into a dredger while nearing the shore at Gheyaghat from Dacope Ghat, said Sardar Masudur Rahman, deputy assistant director of Bagerhat Fire Service and Civil Defence.
On information, firefighters rushed in and recovered body of Sundar.
However, it was not clear whether any other passenger remained missing in the incident, Masudur said, adding that they continued their rescue operation.
Meanwhile, the boat owner jumped into the river as agitated locals chased him for his negligence over the incident.
Later, firefighters rescued him and took him to Rampal Upazila Health Complex.