What does PROTEUS stand for?

Profile Telemetry of Upper Ocean Currents - Marine science

Project to Research Objects Theories, Extraterrrestrials, and Unusual Sightings (EA)

Propulsion Research and Openwater Testing of Experimental Underwater System (SAUS)

Propulsion Research and Open Water Testing of Experimental Underwater Systems (MCD)

Prototype Real-Time Operational Test, Evaluation and User Simulation (SAUS)