The Doctor of Philosophy (Marine Science) is Australia's highest postgraduate research qualification in the marine sciences, designed for exceptional graduates who wish to make an original and significant contribution to knowledge in areas such as marine biology, physical and chemical oceanography, coral reef ecology, coastal geomorphology, fisheries science, marine pollution, and climate-ocean interactions. The degree is structured almost entirely around a single, independent research project supervised by a panel of expert academics, culminating in the submission and examination of a substantial original thesis. Candidates typically spend three to four years conducting primary research that advances scientific understanding in their chosen specialisation, developing expertise that is recognised internationally. The program suits people who are deeply curious about ocean systems and are motivated to investigate unanswered questions — from the molecular biology of coral bleaching to the hydrodynamics of coastal currents or the population dynamics of commercially important fish stocks. Australian universities offering this qualification are connected to some of the world's most significant marine environments, including the Great Barrier Reef, the Southern Ocean, the Indian Ocean, and extensive temperate and subtropical coastal zones, giving candidates unparalleled field research access. Major employers of PhD graduates in marine science include the Commonwealth Scientific and Industrial Research Organisation (CSIRO), the Australian Institute of Marine Science (AIMS), state environment and fisheries departments, the Bureau of Meteorology, Geoscience Australia, the Department of Climate Change, Energy, the Environment and Water, marine environmental consulting firms, aquaculture companies, the offshore oil and gas industry, non-government conservation organisations, and universities themselves as academic researchers and lecturers.

To be admitted to a PhD in Marine Science at an Australian university, applicants are typically required to hold an Australian Bachelor's degree with First Class or upper Second Class Honours in a relevant discipline such as marine science, marine biology, oceanography, environmental science, or ecology — or an equivalent qualification assessed at AQF Level 8 or 9. Some institutions will accept a completed Master's degree by research with a substantial research thesis component as an alternative pathway. The qualifying degree must demonstrate a proven capacity for independent research and must include a meaningful research component, and applicants are generally expected to have achieved a minimum grade equivalent of 70% or higher in their final-year studies. Crucially, prospective candidates must identify and secure the agreement of a suitable academic supervisor (or supervisory panel) before or during the application process, as the PhD is centred on a specific research project that must align with the supervisor's expertise and available resources. Most programs also require applicants to submit a research proposal outlining their intended topic, methodology, and significance to the field. International applicants must satisfy English language proficiency requirements; typical benchmarks include IELTS Academic scores of 6.5 overall (with no band below 6.0) or TOEFL iBT scores of approximately 79–80, though individual institutions may set higher thresholds. Applicants with significant relevant professional experience in marine research — for example, work at AIMS, CSIRO, or state fisheries agencies — may be considered where academic qualifications fall slightly below the standard threshold, subject to faculty higher degree committee approval.