The vessel, with 85 people on board, capsized amid heavy flooding, trapping the passengers, Thickman Tanimu, zonal coordinator for the National Emergency Management Agency, told Reuters.
Anambra state Governor Chukwuma Charles Soludo said in a statement that 10 people had drowned. The head of Anambra State Emergency Management Agency said 15 people had been rescued as of Saturday evening.
The incident happened between 11 a.m. (1000 GMT) and noon on Friday, the agency said.
Area resident and former local government leader Afam Ogene said the boat's engine failed and it was overpowered by waves shortly after it launched.
"It is a locally made boat that can take more than hundred people, unfortunately its engine failed and there was a stampede," Ogene said.
Tanimu said a military disaster response unit from the Nigerian army was assisting the search effort.
Anambra is among the 29 of Nigeria's 36 states to have experienced heavy flooding this year. The waters have washed away homes, crops and roads and impacted at least half a million people.
Ogene said flooding had destroyed the major road linking the eight communities to the rest of the Ogbaru local government area, forcing residents to travel by boat.
Farmers say the rising waters will push food bills higher in a nation where millions have fallen into food poverty in the past two years.
