The observed characteristics of radar sea clutter were described in the previous chapter. This chapter presents some of the empirical models that describe sea clutter characteristics and that can be applied for signal processing design and radar performance predictions. The models are of limited use to the radar designer unless their parameter values can be matched to different environmental conditions, radar characteristics and signal processing schemes. While some headway has been made with direct electromagnetic modelling of the sea surface, nearly all of the models used for practical applications are based on very many measurements of different conditions. The chapter covers models for three main attributes of sea clutter: the normalised radar cross section (NRCS), the amplitude statistics, and the Doppler spectrum. These characteristics were introduced in the previous chapter and their significance will become clear in later chapters of this book.