Wearable Technology in Diving: A Review of Heart Rate and Oxygen Saturation Monitoring for Enhanced Safety and Performance.

Monitoring heart rate (HR) and peripheral oxygen saturation (SpO2) in underwater environments has gained increasing importance due to the expanding popularity of diving activities such as SCUBA diving, freediving, and professional underwater operations. These physiological parameters are critical indicators for detecting adaptive responses and early signs of physiological distress caused by environmental stressors like elevated ambient pressure, hypoxia, cold temperatures, and psychological stress. Although recent advances in wearable sensor technologies offer new opportunities for real-time physiological monitoring underwater, significant limitations persist due to issues such as signal interference, cold-induced vasoconstriction, sensor durability, and the complexity of reliably measuring these parameters in dynamic underwater conditions. Evidence shows HR can fall by more than 50% in freedivers and SpO2 may decline to below 50% during repeated dives, with proposed depth-specific thresholds (e.g., <98.5% at 30 m) serving as early warning levels. This review synthesizes current knowledge on the cardiovascular and oxygenation responses observed during diving, explores the technological challenges associated with underwater HR and SpO2 monitoring, and discusses future directions, including the integration of multisensor platforms and predictive analytics to enhance diver safety and physiological monitoring capabilities. Addressing these technological and methodological gaps holds the potential to substantially improve safety standards and expand the clinical applicability of underwater physiological monitoring systems.