Hearing is fundamental for survival and communication in aquatic organisms, yet the biomechanics of sound detection remain poorly understood due to the small size, internal location, and delicate nature of auditory structures. Traditional approaches such as histology and electrophysiology provide valuable insights but are often invasive, limited to isolated components, or lack the spatial–temporal resolution to capture in situ motion. Recent advances in synchrotron-based X-ray imaging overcome these challenges by enabling high-resolution, high-contrast visualization of soft tissues, even without staining. When combined with tomographic methods, synchrotron radiation allows reconstruction of three-dimensional structures at micrometer to sub-micrometer scales, and with four-dimensional (4D) imaging, it is now possible to capture real-time motion of auditory structures in response to sound. Applications in fishes have revealed otolith and Weberian ossicle dynamics under controlled acoustic fields, progressing from qualitative visualization to submicron quantitative displacement analysis. Comparable methods hold promise for invertebrate systems such as statocysts and mechanosensory organs. Synchrotron bioimaging represents a transformative tool for linking auditory structure, function, and ecology, providing new perspectives on how aquatic animals perceive and respond to underwater sound.