Besides the open sea, ports, fairways, pilot services, and ice-breaking are the main maritime infrastructure components. Marginal costs of maritime transport can be divided into the following groups: emissions to water and air, accidents, and costs related to infrastructure usage. The first marginal cost type is the occurrence of negative external effects to third-men outside the transport system. The marginal costs from infrastructure use are related to the parts that invest, maintain, and provide the services in themselves as well as to the users. The latter part is affected by restrictions in capacity, which can affect the user costs of the services. This report considers all these marginal costs components, except emissions to air. The basic purpose of the report is to narrow down the state of knowledge regarding: - Marginal cost pricing in theory; - Empirical research regarding marginal cost pricing; - Review availability of data and how institutional conditions affect the possibilities for implementation of marginal cost based pricing. The scope of the report is limited to the state of knowledge concerning maritime infrastructure of the types mentioned above and external effects from accidents and emissions to water. A secondary purpose of the report is to give suggestions for further research based on the authors' view of the state of knowledge.