Adaptive Optics for Underwater Optical Communication and Imaging: A Critical Review and Impairment-to-Adaptation Framework

Underwater optical communication and imaging are degraded by absorption, scattering, refractive index fluctuations, interface aberrations, and platform motion. These impairments require different measurements and corrective actions. This critical narrative review evaluates physical wavefront correction, including Shack–Hartmann sensing with deformable-mirror or spatial-light-modulator control, sensorless optimization, phase conjugation, and learning-assisted estimation, alongside aperture averaging, beam tracking, and computational or link-layer adaptation. An impairment-to-adaptation framework connects the dominant disturbance to an available observable, an intervention, a task-specific metric, a validation setting, and a deployment constraint. Evidence from analytical studies, controlled-water tests, integrated prototypes, and field systems is interpreted separately; adjacent communication methods are not conflated with adaptive optics. A quantitative design example illustrates the roles of coherence time, sensing-to-actuation delay, and net communication benefit. Within the reviewed corpus, wavefront characterization and controlled-water correction are documented more extensively than moving-platform, open-water, closed-loop adaptive optics, for which independent validation remains limited. The review provides practical criteria for selecting, combining, and evaluating correction techniques without implying a universal performance ranking.