The dynamics that underlie the generation of epizootics in marine ecosystems still lack the equivalent level of description, conceptual understanding, and epizootiological modeling framework routinely present in the terrestrial environment. Here, we propose a theoretical basis for the transmission dynamics of marine infectious diseases (MIDs) by means of a series of compartmental models, expressed in a comprehensive formulation adapted from Kermack and McKendrick's mathematical theory of epidemics. The models represent the dynamics of a variety of host-pathogen systems including transmission by direct contact not only between live animals, but also between dead animals and living susceptible hosts. We also include cases where transmission occurs via particle transport through the water column and uptake by contact or filtration of waterborne infective pathogens released to the water column by live or dead infected animals. From these models, we formulate the basic reproduction number Ro using the next generation matrix procedure. The sensitivity of the series of Ro models to their parameters was analyzed to explore their relative importance and interaction in determining the potential for epizootic development. A priori, systems where the transmission involves a variety of processes, such as the death of infected animals, dead animals releasing pathogens in the water, and filter feeders accumulating them, an epizootic should be less probable than for contact-based diseases for the same population density. This contribution covers the mathematical basis for the dynamics and epizootiology of a diverse array of MIDs, focusing on the initiation and termination of epizootics.