A new device was developed and tested in a series of diving experiments investigating the physiological effects of immersion on military divers for long periods (8 h to 12 h). During these experiments, the body temperature (core and skin) and electrocardiogram (ECG) of the divers were recorded and monitored in real time. The system developed for this purpose comprised a modified VitalSense temperature monitoring device from Philips Respironics and a one-channel ECG housed in a pressure-proof case. Recorded data were transmitted wirelessly to a PC. The recording and visualisation software was developed under National Instruments LabWindows.