Twenty fishermen were missing and thousands of families fled their homes as strong winds and heavy monsoon rains swept Bangladesh, police and officials said on Sunday.
Four boats with 36 fishermen aboard sank in the Bay of Bengal during a storm on Saturday, police said. Sixteen were rescued and the rest are missing, said Kabir Ahmed, president of the Fishing Boat Owners' Association in Cox's Bazar, 400 km (240 miles) southeast of the capital Dhaka.
"The storm struck our fleet about 10 km from the Cox's Bazar coast and suddenly a huge wave slammed onto us, sending four boats deep under water," survivor Abdullah told reporters.
"I swam like a fish, gasping for breathe. When I almost lost all hope, crew from other boats saw my raised hands and came to my rescue."
Hopes were fading of finding any more survivors.
"The sea has been rough with rain and winds still continuing. If they are not found alive by Monday morning, we should presume they are dead," a local official said.
In the coastal area of Teknaf, one woman died after she was swept into the sea on Sunday, police said. On Saturday, two people, including a child, were killed when mudslides triggered by rain buried their home in Cox's Bazar.
On the island of Hatiya, some 25,000 people fled their homes and took refuge on a flood protection embankment, island administrator Mohammad Zahidul Islam said. Hatiya is about 15 km from the coast.
"The situation here is growing more desperate every day as telecommunications with the island have virtually broken down with most of its 64 telephones out of order," said local reporter Krishan Chandra Majumder.
A Dhaka weather official said on Sunday a very active monsoon had dumped more than 200 mm (eight inches) of rain in Bangladesh's southeast since Saturday and more was expected.
The rain also flooded low-lying areas and some streets in Dhaka.
Most Bangladesh rivers including the Jamuna, Padma, Brahmaputra and Meghna were rising but flowing below danger levels, flood monitoring officials said.