This STL file package allows directed water flow in order to offer both thrust as well as pitch and yaw. 
 
The supplied parts are designed to fit a brushless motor with mounting holes spaced at 25mm. It is recommended that the motor be housed in a watertight compartment, and you can easily extend your driveshaft to whatever length required and use the motor mounting bracket as a secondary bushing mount instead.
 
The package includes a propeller sized for a 1/8" diameter shaft.