Huang, LoulinTun, Thein ThanPreece, Mark Anthony2026-01-072026-01-072026-01-07Journal of Marine Science and Engineering, ISSN: 2077-1312 (Print), 14(2), 115-115. doi: 10.3390/jmse140201152077-1312http://hdl.handle.net/10292/20453In many aquaculture farms, Unmanned Underwater Vehicles (UUVs) are being deployed to perform dangerous and time-consuming repetitive tasks (e.g., fish net-pen visual inspection) on behalf of or in collaboration with farm operators. Mostly, they are remotely operated, and one of the main barriers to deploying them autonomously is the UUV localisation. Specifically, the cost of the localisation sensor suite, sensor reliability in constrained operational workspace and return on investment (ROI) for the huge initial investment on the UUV and its localisation hinder the R&D work and adoption of the autonomous UUV deployment on an industrial scale. The proposed system, which leverages the AprilTag (a fiducial marker used as a frame of reference) detection, provides cost-effective UUV localisation for the initial trials of autonomous UUV deployment, requiring only minor modifications to the aquaculture infrastructure. With such a cost-effective approach, UUV R&D engineers can demonstrate and validate the advantages and challenges of autonomous UUV deployment to farm operators, policymakers, and governing authorities to make informed decision-making for the future large-scale adoption of autonomous UUVs in aquaculture. Initial validation of the proposed cost-effective localisation system indicates that centimetre-level accuracy can be achieved with a single monocular camera and only 10 AprilTags, without requiring physical measurements, in a 115.46 m3 laboratory workspace under various lighting conditions.© 2026 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.400706 Field robotics401503 Ocean engineering0405 Oceanography0704 Fisheries Sciences0911 Maritime Engineering3005 Fisheries sciences3709 Physical geography and environmental geoscience4015 Maritime engineeringUnmanned Underwater Vehicle (UUV)cost-effective UUV localisationAprilTag detectionaquaculture infrastructureJournal ArticleOpenAccess10.3390/jmse14020115