The hydrospatial community has advanced the use of Free and Open-Source Software (FOSS) in the ocean mapping workflow by developing new solutions and adopting tools originally developed for other applications. These specialized tools allow users to conduct common tasks in hydrography without the need for commercial software, but, most importantly, to perform tasks for which no proprietary solutions exist. Besides the above tools, there is a plethora of additional FOSS for geospatial applications (FOSS4G) that could be used in ocean mapping. Some form of documentation on the aforementioned tools exists. However, a comprehensive study of their capabilities and performance in ocean mapping is not yet available. It is not surprising that the use of FOSS4G within hydrographic offices remains limited. To fill this gap, we are conducting a project that aims to investigate the functionalities of the available FOSS4G and raise awareness about the potential benefits of their use in the domain. After identifying and evaluating the available FOSS4G for their usability in ocean mapping, we tested the selected FOSS for Ocean Mapping (FOSSOM) in a mapping campaign near the Canary Islands, Spain. Multibeam bathymetry and backscatter data from the seabed and the water column in the area were acquired as part of mapping the Spanish Exclusive Economic Zone (EEZ). We demonstrate that FOSSOM may be used to optimize survey design, troubleshoot and resolve multibeam system performance issues, derive products, and enhance data visualization and dissemination. A workflow that incorporates the unique capabilities of FOSSOM is proposed with the aim to streamline planning-to-product workflows.