Based on the well acquaintance with the hydrogeological conditions in the Beihai Peninsula, Guangxi, China, the authors conceptualize the first confined aquifer in this area into a vertical three-layered non-stationary flow model with the aquifer submarine outlet-capping and the leakage through the aquifer’s roof. The analytical solution to this model is applied to analyze the tidal and piezometer data in a coastal aquifer of the Beihai Peninsula in this paper. The aquifer parameters are estimated using least-squares objective function with novel penalty functions incorporating known information.