Azmal aged 41, accompanied by a boatman had gone to SK Long Balawa to pick his fiancée to go to Belaga town in a longboat which overturned due to strong current.
Belaga OCPD DSP Bakar Sebau said according to reports made, Azmal and the two successfully swam to the shore.
As they reached the river bank, Azmal who was an asthmatic patient became breathless.
He collapsed and died.
His remains were brought to the Belaga hospital for a post mortem.