tesla's wardencliffe tower wanted to transmit power to the ionosphere. if it worked you could put a receiving tower on each cargo ship, and discharge through the water. goodbye sea life though, which is our problem since they produce a lot of oxygen and food for us.

i'm thinking of an undersea cable running on the sea floor with periodic vertical cables tied to floating platforms for cheapness, or oil rig type platforms if the cables are too heavy. then the boat only needs to charge its batteries there long enough to reach the next charging rig.

you would have at least two charging points for each direction of travel, that way boats travelling in opposite directions are not blocked.