A ship employing a buoyant propulsion system. A preferred such ship comprises a superstructure, a backbone, and a sub-structure. The backbone supports the superstructure. The sub-structure depends from the backbone and adapted to float the backbone and the superstructure above liquid water. The sub-structure includes one or more buoyant propulsion units. Each buoyant propulsion unit comprises an endless track having a plurality of associated paddle members and is adapted for elongate rotary motion of at least portions of the associated paddle members through the water. Each buoyant propulsion unit further comprises a race-roller-bearing assembly for transmitting load imposed by the superstructure to the track. Preferably, the one or more buoyant propulsion units are adapted to float the backbone and the superstructure substantially above the water.