We describe the development of a novel wrist-mounted apnea dive computer. The device is able to measure and display transcutaneous oxygen saturation, heart rate, plethysmographic pulse waveform, depth, time and temperature during breath-hold dives. All measurements are stored in an external memory chip. The data-processing software reads from the chip and writes the processed data into a comma-separated values file which can be analysed by applications such as Microsoft Excel™ or Open Office™. The housing is waterproof and pressure-resistant to more than 20 bar (2.026 MPa) (breath-hold divers have already exceeded 200 metres' sea water depth). It is compact, lightweight, has low power requirements and is easy to use.