The period from 1980 to 1990 marks a convergence of acoustic tomography and propagation-based observations with satellite- and in-situ sensing, forming an integrated observing framework for mesoscale ocean structure. Satellite altimetry matured into a core tool for mapping dynamic topography and mesoscale variability, aided by Seasat and GEOS-3 calibration and refined mean sea surface products. Instrumentation advances expanded in-situ measurements and seafloor sensing, including deep-sea differential pressure gauges, multibeam sonar, and robust acoustic transmission systems, while global data products and climatologies provided essential baselines. Repeat-track altimetry and cross-instrument synthesis illuminated mesoscale eddy dynamics and Gulf Stream–related topography, enabling the capture of rings, eddies, and associated topographic features. Historical Significance: The era established a practical, multi-modal paradigm for observing ocean processes, integrating acoustic, altimetric, and in-situ measurements into cohesive baselines and data products, which underpinned later ocean-observing networks and modeling frameworks. Foundational breakthroughs included the development of geoacoustic models of the seafloor, compact sound-speed formulations for broad temperature–salinity–depth ranges, and standardized in situ calibration methods for shipboard acoustic Doppler current profilers. These innovations, along with high-resolution turbulence sensing using pulse-to-pulse coherent sonar, created enduring capabilities for sonar performance, seabed characterization, and turbulence research, shaping subsequent decades of oceanography.