The invention generally relates to hand-held underwater propulsion systems. In certain embodiments, systems of the invention include a hand-held body having a water-tight compartment. There is a motor housed within the water-tight compartment. There are a plurality of propeller blades located at a front portion of the body and coupled to the motor. Each blade includes a retracted configuration and a deployed configuration, and in the deployed configuration, the blades are biased away from the body.