NavySim (Navy Simulation), formerly NSTMSS (Naval Surface Tactical Maneuvering Simulation System), is a free academic distributed naval simulation suite built on the High Level Architecture (HLA, IEEE 1516-2025 / HLA 4) with the Fora RTI. It includes MEKO-class and Knox-class frigate ship-handling simulators, a C2SIM exercise manager and scenario editor, an environment federate and a federation monitor, and is used for HLA research and naval cadet training in formations and maneuvering. Documentation: https://otopcu.github.io/navysim-site/