Résumé : Two key facilities for the INPEX-operated Ichthys LNG project; the central processing facility (CPF) and floating production, storage and offloading (FPSO), were constructed in South Korean ports and towed to offshore Australian waters. To meet regulatory requirements for their importation, and mitigate potential invasive marine species (IMS) introduction, species-specific biofouling risk assessments were completed, and a series of management measures implemented. Risk assessments quantified the theoretical likelihood of the facilities introducing IMS via biofouling. The assessments considered (but were not limited to) the type of antifouling coating (AFC), time alongside, niche areas, and likelihood of IMS surviving in offshore waters at the Ichthys Field if translocated. The two facilities had different AFCs on their submerged hulls (CPF: biocidal, FPSO: non-biocidal). The theoretical risk of introducing IMS to Australian waters was considered ‘uncertain’, requiring completion of an extensive pre-mobilisation cleaning program in-water (CPF >600 dive hours and FPSO 2381 dive hours). The FPSO was cleaned twice due to a delay and recolonisation on the non-biocidal AFC. To determine the most efficient cleaning methods, various in-water cleaning technologies were trialled. Due to the size and complexity of the facilities, biofouling inspectors were deployed throughout the operation to increase confidence in the outcomes. After the arrival of the facilities at the Ichthys Field, dedicated underwater surveys were conducted to assess biofouling communities and collect specimens for molecular analysis, using a specially designed sampling tool. The associated outcomes demonstrated that the risk was acceptable and had been reduced to as low as reasonably practicable, validating the novel approach taken.