This work presents a novel hydrokinetic turbine (HKT) powertrain utilizing a Vienna rectifier for improved efficiency and reduced size. Unlike traditional HKT powertrain with a passive rectifier and DC/DC converters, the proposed powertrain integrates a Vienna rectifier as both a gen-side rectifier and step-up converter, enabling high-voltage DC bus for offshore applications. The dynamic current control strategy for the proposed powertrain is explained, which can achieve optimal power output by changing the tip speed ratio (TSR) across varying water velocities. Last, initial hardware experiments are conducted with the generator-motor setup and the converter system. Results demonstrate the system functionality and high performance of the proposed powertrain.