Abstract: An underwater location system (16) is disclosed having a plurality of locator modules (18), each capable of finding the relative range and bearing of other modules. The modules may be diver mounted, placed on movable objects such as a boat (14) or on fixed positions such as the sea floor (12). Range and bearing to each module of the system is displayed, upon request, on a console (20) which may be hand held or mounted in a diver's instrument console. Each module can interrogate other modules with an acoustic pulse which is answered, after a unique time delay stored in each module, by an acoustic response pulse. Response pulse sources are identified by their arrival in a time detection window set by their unique time delay. Range to each identified transponder source is calculated from a receipt time within each detection window.