The C-Master MKII is an affordable solution for military divers requiring accurate underwater positioning. Using advanced dead reckoning, GPS, DVL, or IMU/INS, the C-Master MkII provides operators underwater navigation with high-precision and real-time performance. The ORCA, a Low Probability of Intercept acoustic communication network, can be added to the C-Master MKII and carried by small underwater vehicles or divers. Both built-in message distribution protection and multi-hop mechanisms increase the reliability of the network and the connectivity between nodes, providing a solution for non-line-of-sight scenarios. ORCA supports SMS and navigational control messages, allowing the user to create his own mission status.