At least 38 passengers survived the accident that killed at least 21 others, while the remaining 34 passengers were missing, according to data from the health post at Tanjung Bemban in Batam.
One of the survivors, Haryanto, 51, told The Jakarta Post that the boat departed from Selingi, Johor Bahru, at 3 a.m. heading to Batam.
"After two hours of sailing, the boat was struck by strong waves and heavy downpour," he said.
A search and rescue team has been deployed to find more survivors in the accident.
Riau Islands Police chief Brig. Gen. Sambudi Gusdian said that police investigated those responsible for the accident, suspecting that the boat was reportedly overloaded and the trip was organized illegally.