The concept, design and testing of an electric thruster for underwater propulsion based on the electro osmotic principle is presented. A unique feature of the proposed electro-osmotic thruster (EOT) is that it has no moving parts, enabling robust stealthy operation and the potential for working under extreme underwater pressures. Furthermore, the EOT is unaffected by magnetic fields as it does not require metals in its fabrication. In a particularly extreme operation test, a small EOT was immersed in an ultrasonic bath and demonstrated normal operation in such an environment. In another test, multiple EOTs were aligned to work in parallel to increase packing efficiency. In a large-scale test, the EOT successfully propelled a small 5 kg unmanned underwater vehicle (UUV) at 2.2 centimeters per second. This experiment was performed using a twenty- fifth of the EOT's maximum potential thrust that could be available if it were to be mounted in a REMUS 100 autonomous underwater vehicle (AUV) size platform. The EOT is the first underwater thruster to continue the abandoned work of magneto-hydrodynamics in finding low wake steady-state propulsion.