The victim, identified as Rohan Parab, died due to drowning and his body could be retrieved around one hour after the accident, police said.
"Parab was declared dead on arrival at Goa Medical College and Hospital," Old Goa police officials said.
The mishap occurred when the bike hit a car at Ribandar village. The impact of the collision was so severe that Parab was flung off the motorcycle, fell into the river and died due to drowning, police said.