Langmuir supercells (LSCs) are intense full-column energy mode in the coastal shallow water, which is caused by the resonant effects between surface and bottom interfaces.  We investigate turbulent structures and their generation mechanisms under varying wind–wave and current conditions in this dual-boundary layer system using a modal decomposition framework. Starting from the Craik–Leibovich (CL) equations, we derive the transfer function and show that inclusion of the vortex force transforms the governing equations from a one-way-coupled system into a two-way-coupled system. Non-linear effects due to Reynolds stress are further incorporated using the Boussinesq eddy-viscosity hypothesis. We impose representative mean-flow and eddy-viscosity profiles under typical conditions as the background forcing. These profiles are extracted from a series of large-eddy simulations (LES) to characterize fully developed LSCs. The resolvent analysis method is applied to investigate the generation and persistence of turbulent coherent structures in the fully developed state. Finally, the generation mechanism of full column turbulence due to preferential coupling condition between wave-current interaction and bottom shear is presented.