Preface The 4th MSAT Conference “Scaling Up Ocean Action Based on Science and Innovation for the Implementation of the Blue Economy” held in Bandung, West Java, Indonesia on the 26-27th of October 2023 was part of a conference series held biennially since 2017 (https://msat.fitb.itb.ac.id/). The 4th MSAT conference on maritime science and technology targets the United Nations Sustainable Development Goals (SDGs), specifically the SDGs no 13 and 14 (Climate Action and Life below water), as well as no. 1 (No Poverty), no. 2 (Zero Hunger), and no. 7 (Affordable and Clean Energy) through the maritime section, especially as our country is the second-largest coastline in the world with 60% of our citizens living in the coastal area. With those goals, MSAT 2023 places a spotlight on the critical role of science and innovation in fostering the blue economy. The conference theme is not only timely but also holds the promise of unlocking new horizons for oceanic prosperity. The conference builds upon a strong legacy. The 1st MSAT Conference proceeding (Volume 62) was published at IOP on 06 July 2018 (https://iopscience.iop.org/issue/1755-1315/162/1); our second conference proceeding (Volume 618) was published at IOP on 21 December 2020 (https://iopscience.iop.org/issue/1755-1315/618/1); and our third conference proceeding (Volume 925) was published at IOP on 06 December 2021 (https://iopscience.iop.org/issue/1755-1315/925/1). These volumes showcase a wide range of research findings encompassing “Ocean-Atmosphere Dynamics, Marine Hazard and Coastal Degradation, Marine Resources, Conservation and Integrated Coastal Zone Management (ICZM), and Marine Geodesy and Satellite Oceanography” as discussed at the sessions of each conference. These three conference proceedings document the journey of MSAT, and serve as a testament to the commitment of the maritime community to push the boundaries of knowledge and technology. They have not only advanced the field of ocean science but also contributed to the global cause for sustainability. Following the success of the previous conferences, the 4th MSAT continued the tradition of excellence. Building upon the momentum from the online edition of the 3rd MSAT due to the COVID-19 pandemic, this conference marked a welcome return to an in-person format. However, an online option was still accommodated to ensure wider participation. The conference was jointly organized by the Faculty of Earth Sciences and Technology - Institut Teknologi Bandung, the Marine Technology Cooperation Research Center (MTCRC), and the Indonesian Association of Oceanology (ISOI). It attracted a diverse group of participants, including scientists, students, and stakeholders from Indonesia and abroad. The total number of people who attended the 4th MSAT 2023 was 208 people, consisting of 136 participants, 38 committees, 17 keynote and invited speakers, and 17 moderators. The first day of the MSAT 2023 conference, held on October 26th, 2023, attracted international participation thanks to its well-regarded speakers from around the globe (Singapore, Malaysia, Spain, Japan, Korea, and Australia). The opening ceremony commenced with welcoming remarks from the Dean of the Faculty of Earth Science and Technology, Prof. Dr. Irwan Meilano, S.T., M.Sc., and Chairman of ISOI, Prof. Dr. Agung Dhamar Syakti. Additionally, a video message was delivered by a representative of the Ministry of Maritime Affairs and Fisheries. Following the opening, Prof. Yoshiyuki Kaneda from the Institute of Education Research and Regional Corporation for Crisis Management Shikoku (IECMS) at Kagawa University, Japan, presented a plenary session lecture. This was succeeded by a talk from Prof. Dr. Irwan Meilano himself, followed by a series of five parallel mini-symposia sessions. List of Steering Committee, Scientific Committee, Advisory Board, Organizing Committee, Editorial Committee and Photo documentation are available in this Pdf.