The accident took place Wednesday evening near the small town of Theres, about 20 kilometres east of Schweinfurt. The police said the teen was riding a Yamaha, making it unclear if he was on a sit-down waverunner craft.
The youth was slammed onto stones that make up the divider, sustaining heavy injuries. He died not long thereafter. Onlookers in other boats rushed to the scene and pulled the boy's body out of the water.
Police are still uncertain why the boy rammed into the barrier at full speed. He was not in possession of a licence to ride the watercraft, which is mandatory in Germany. The minimum age to ride a jet ski or waverunner in Germany is 16.
The vehicle's owner may now be liable for the youth's death under German law. The waterway police and local prosecutors are investigating the accident.