The advent of offshore exploration for oil and gas during the 1970s created a need for very accurate underwater position fixing for survey activities such as searching, mapping and photography, and for work tasks such as pipe laying, surface rig positioning, underwater structure positioning, towfish positioning, remotely operated vehicle (ROV) navigation, subsea construction, mining, drilling and a vast range of other applications. The precision required dictates the use of underwater acoustic navigation and tracking techniques, and the best known of these employ arrays of hydrophones, beacon (also called pingers), transponders (receiver-transmitters) and responders (transmitter- receivers). For most of the tasks listed above the positioning is carried out only after a series of procedures to fix the position of the array on the sea bed; these may include transponder deployment, array baseline calibration and possibly absolute calibration in terms of geodetic co-ordinates by integrated satellite, surface and underwater data telemetry. In this paper, we consider how techniques and systems developed for industrial applications may be adapted for tracking echo-locating cetaceans (dolphins, porpoises and whales), in particular the principles of position fixing in three-dimensional space in real time. This is a problem that presents a serious engineering challenge.