During 1960 to 1966, the field converged on wave-driven, potential-flow based methods to tackle fluid-structure interactions. Researchers demonstrated that a traveling wave along a slender body can produce propulsion with intriguing efficiency advantages, and that a traveling wave on a flexible plate in a potential flow can generate thrust without external forcing, establishing the groundwork for bio-inspired propulsion and fluid-structure interaction studies. Variational formulations and Lagrangian perspectives provided a cohesive mathematical backbone, enabling systematic derivation of governing equations and boundary conditions. The development of expressions for exciting forces on bodies in waves using far-field potentials, together with connections to macroscopic hydrodynamics through correlation functions, broadened the computational toolkit for wave loading and turbulence considerations. Collectively, these advancements fostered a cohesive framework for analyzing unsteady hydrodynamics in marine contexts.