Cognitive risk during underwater exposure: from environmental stressors to assessment and context-aware monitoring

Underwater exposure imposes a distinctive cognitive burden because divers must maintain performance while environmental and physiological safety margins can change rapidly. Safe performance depends on attention, psychomotor speed, executive control, working memory, spatial orientation, metacognition, and decision-making, each of which may be influenced by pressure, breathing gases, respiratory load, immersion, thermal stress, fatigue, and individual susceptibility. Evidence from recreational, technical, breath-hold, and saturation diving remains difficult to synthesize because studies differ in exposure mode, gas composition, timing, task selection, ecological validity, and operational endpoints. This narrative state-of-the-art review addresses three questions: which stressors shape cognitive risk, how risk is currently assessed, and how selected signals might contribute to future context-aware estimation without adding unsafe task burden. We describe the literature-identification strategy, define cognitive risk as a probabilistic and baseline-referenced state rather than a single test abnormality, and map vulnerable domains to operational hazards such as delayed response, navigation error, unsafe gas decisions, missed alarms, and delayed recovery. We critically evaluate behavioral tasks, CFFF, EEG/ERP, HRV, electrodermal activity, NIRS, respiratory CO₂ monitoring, and wearable platforms, emphasizing feasibility, signal quality, nonspecificity, synchronization, individualized baselines, and validation against operational outcomes. Finally, we propose a staged pathway from dry chamber validation to wet-chamber or planned-pause testing and then to occupational or saturation settings. Selected physiological and behavioral signals may contribute to cognitive-risk estimation only after transparent interpretation and prospective validation against meaningful endpoints.