A boat would be much more difficult. The North Sea has strong tides with associated strong and varying currents. It falls "dry" for six hours every 12 hours. Besides, it's Germany: To keep in style, the boat would have to be a u-boat.
I think to make the boat option viable it would have to be a submersible of some kind. And then it could hook up to an underground, automated system that launches a quadcopter drone out of a silo for local delivery.