Offshore wind (OSW) is an important component of the transition to renewable energy in the USA. OSW projects generate electromagnetic fields (EMFs), which may impact marine organisms. In pre-construction assessments of these impacts, modelled EMFs are compared with literature-derived effect thresholds for sensitive marine organisms. However, it is frequently unclear whether some literature-derived effects are meaningful at a population level. In the absence of data, biologically detailed models, such as agent-based models (ABMs), can tie exposure and effects together. Here, we describe an ABM that simulates an electrosensitive organism, little skate, swimming in the presence of a direct-current magnetic field generated by undersea OSW cables. The model simulates behavioural effects from EMF exposure on individuals in a modelled population and translates the effects into an energetics basis, providing a quantifiable metric of the effect of exposure on population viability. Through a proof-of-concept application, we show that ABMs can help support EMF impact assessments by helping to evaluate potential exposure effects in a context relevant to fisheries management.