This publication is part of the IPIECA-IOGP Good Practice Guide Series which summarizes current views on good practice for a range of oil spill preparedness and response topics. The series aims to help align industry practices and activities, inform stakeholders, and serve as a communication tool to promote awareness and education. This guide aims to provide stakeholders such as responders, regulators, statutory consultees, industry, NGOs, oil spill response organizations and academia with an overview and guidance on good practice with regard to the fundamental principles of using in-water surveillance.