More than 40 people are feared dead after their boat capsized in bad weather on Lake Albert.
Some 19 bodies are said to have been recovered so far, with 34 passengers rescued by police.
The authorities are estimating at least 75 passengers were on board the boat which was travelling from the town of Bugoigo to Panyamurro early on Monday.
Dozens die in boat accidents on Uganda's lakes each year. Police usually blame overcrowding.
"We are still searching. We think at least 40 must have drowned," regional police commander Grace Turyagumanwe told Reuters news agency.
The police say the boat had stopped at various landing sites along the lake shore picking up heavy loads of salted fish.
Some passengers are reported to have survived by holding on to the capsized boat.
Boats travelling on the lakes in this region are often overloaded and accidents are frequent.
In 2002 more than 100 people died on Lake Victoria.
As a result there have been calls for lifejackets to be compulsory - however despite the frequent loss of life the law has not been passed.