Generating electricity from renewable energy sources is part of the solution to achieve the drastic reduction in anthropogenic emissions of carbon dioxide that is required to meet climate change objectives. The potential contribution of offshore renewable energy sources for maritime nations such as the United Kingdom, with its abundant offshore wind, wave and tidal resource, are significant. However, the cost of offshore renewable energy is typically higher than conventional generation methods. The installation costs largely driven by the charter costs of construction vessels can account for approximately 25% of the overall capital expenditure, whereas maintenance vessels and logistics contribute to around 45% of the operational expenditure. Here a versatile, time-domain, discrete event simulation software has been developed that can be used to study the behaviour of a diverse range of marine operations related to the construction, maintenance and decommissioning of offshore renewable energy projects. Various operational strategies can be simulated with the intention of identifying causes of delay and selecting the best available strategy. A Coloured Petri Net has been used to model the workflow of the marine operations, where the transition nodes on the net represent the activities. The stochastic timings of the transitions are sampled using a combination of an operational window array generated from historic meteorological and oceanographic time series and by random sampling of probability distributions to represent other causes of delay. The software has been applied to a range of industrial projects, where the ability of the program to analyse the probabilistic performance of different operational strategies has been shown to reduce the cost of marine operations of one work-package of a particular project by over £5 million around 9% of the vessel charter costs. It is expected that through the deployment of software, like the one developed here, the cost of marine operations can be reduced across the life-cycle of an offshore renewable energy installation with the effect of lowering the cost and therefore hastening the expansion of offshore renewable energy as a major source of electricity.