An underwater investigation system may include a host ship, a UUV including a propulsion device and a steering device, and at least one sonar system. The system may further include a guidance controller configured to initiate sonar range measurements between the host ship and the UUV using the at least one sonar system, and estimate a respective UUV position state relative to the host ship at the initiation of at least some of the sonar range value measurements to define a series of successive UUV position state estimates. The guidance controller may be further configured to update UUV position state estimates in the series based upon completion of their respective sonar range measurements, propagate the updates to subsequent UUV position state estimates in the series, and control the propulsion device and the steering device to guide movement of the UUV relative to the host ship based upon the updated position state estimates. The system thereby provides relatively precise guidance and navigation capabilities to maneuver the UUV relatively long distances away from the host ship.