The enormous and growing scale of human intervention in coastal processes is driven by a short-sighted societal desire to protect property in the face of shoreline recession. Underpinning this effort in both the design of engineering interventions and the amelioration of their impacts is the application of numerical models that purport to simulate and predict coastal processes. Coasts are complex systems in which (1) waves, currents, tides, and wind operate on a (2) finite or changing volume of sediment of specific character (3) within a particular geological context. Feedbacks exist within and between these three domains, and all are temporally and spatially variable. The simplifications and assumptions involved in reducing this complexity to equations and numerical models cause a deviation from reality such that models are unable to provide realistic predictions of coastal behavior. Nonetheless (and despite criticism from geologists), models have become entrenched in coastal engineering practice and are now a standard weapon in society's assault on the world's coasts. In this paper, we chart the development of several widely used models, highlight their shortcomings, and speculate on why they remain in use. The disconnect between reality and the mathematics of coastal process models is extreme, and a fundamental reassessment is required.