Improvements in hydrokinetic floating power plant efficiency are obtained by optimization of (1) gaps z and z′ between the hydrokinetic driving engine blades and internal sidewalls and floor of the working channel of the driving engine; (2) the ratio of the submerged part of blade height in liquid and part of blade height above the liquid surface; (3) the angles of inlet side planes and bottom planes of a confusor and the outlet side planes of the diffusor; and (4) distance t between blades and number n simultaneously submerged blades in the working channel of the driving engine.