By this autumn at the latest, Deutsche Post wants to use a special solar ship to transport parcels across the Spree to the districts - possibly even in the summer.
Talks with the districts were still ongoing, the company told the German Press Agency.
Among other things, the necessary infrastructure for loading and unloading the ships must be created at the landing stages.
"We plan to initially use at least one solar-powered ship on the Spree," it said.
"The starting point will be Berlin's Westhafen."
The extent to which packages can be delivered in this way has not yet been decided.
"Measured against the total daily volume, however, it will be comparatively small at the beginning," said the post only.
The plans for a solar-powered mail ship were already known in mid-May.
From the piers, the deliveries are to be reloaded onto transport vehicles and distributed.
The project is part of a joint research project in which the Technical University of Berlin (TU) is also involved.
"In metropolitan regions with an existing waterway infrastructure with low utilization, the shipping mode of transport usually offers massive free capacities for the shift of freight traffic from the congested roads to the water," it says there.
According to Post, the vision is to use autonomous, electrically operated ships at some point.