The Underwater High-Dose Gamma Probe (UHDGP) is designed to measure gamma doserate or display counts over a predetermined time interval. The UHDGP comprises of an anodised aluminium housing, gm tube, radiation-hard silicon detectors, signal processing electronics, data logger, power supply and RS485 communications circuitry. The UHDGP is capable of operating autonomously for a period of 100 hours or can be monitored remotely by means of a portable instrument (e.g. JCS NMS014) or optional handheld/personal computer (running the JCS Data Logging Application).