The boat was on its way to Narsingdi, 100km from the Bangladeshi capital Dhaka, when it sank, drowning 11 people, officials said.
More than 400 people have died so far in three weeks of flood havoc in Bangladesh while the total toll in South Asia has crossed 1000, according to official estimates.
About two-thirds of the low-lying and impoverished nation is under water in the worst flood in 15 years.
Disaster-relief officials said new deaths were reported from all over the country from drowning, disease and snake bites and from house collapses.
Floods have also killed as many as 630 people in India's eastern state of Bihar and in the north-eastern state of Assam.
In Bihar, state relief minister Ram Vichar Rai said more than 320 bodies had been found in remote areas in the last 72 hours as flood waters receded. The toll could rise sharply in coming days, he said.
This year's death toll in Bihar was the highest in three years of floods. State relief and rehabilitation officer Tewari said he expected the toll to rise as rescuers reached remote parts of the impoverished state.
Meanwhile, the death toll in the Indian state of Assam rose to 170, officials said. About 12 million people had been affected by the floods, which had disrupted essential supplies.
"There is an acute scarcity of baby food and over 500,000 babies affected during the floods are starving," Assam Health Minister Bhumidhar Burman said.
"There is an acute scarcity of baby food and over 500,000 babies affected during the floods are starving,"
Health Minister in the Indian state of Assam
More than 200 doctors and paramedics had been called in to battle disease, he said.
The situation in Bangladesh is even more worrisome. Floods have inundated large parts of the capital, forcing thousands of families into shelters where authorities were distributing food and drinking water.
Officials said more than 100,000 people had moved into schools and high-rise buildings in the capital, and thousands more were expected to join them.
"There is hardly any room left for them," said an official in the Old Dhaka area. Some shelters had been flooded.
A city soccer stadium had been turned into a shelter for about 10,000 people.
"We came here from slums around the city but life is even harder here, with little food but no electricity, no toilets and mosquito bites at night," said Sufia Begum, a woman who has taken shelter at the stadium.
With the number of people nearly doubling in one Old Dhaka shelter in the 24 hours to Tuesday afternoon, food and medical supplies were running short. Streets were waist-deep in water and boats had replaced rickshaws.
Dhaka's sewerage system has stopped functioning and water-borne diseases are rampant.
"Conditions are getting worse every day. The water is rising and bringing in more filth," said government official Abu Kalam. "We are living in an open sewer."
Boats have replaced rickshaws in
Officials have told people not to eat fish caught in floodwaters.
Health officials say at least 60 people have died of diarrhoea and other water-borne diseases, while doctors say the flow of patients - most of them children - will rise.
It is the worst flooding in Bangladesh since 1988 when about 3500 people died.
This year's floods have left more than 10 million people homeless.
Agriculture officials say paddy and other crops worth $380 million have been lost.