The multidisciplinary investigation of gas in marine sediments is essential for elucidating Earth's climate evolution and projecting future patterns. Light hydrocarbons and carbon dioxide present in marine sediments provide valuable insights into historical environmental dynamics of the carbon cycle and its anthropogenic influences. Various geophysical methods in combination with seafloor drilling techniques are used to identify and characterize the various gas reservoirs (free gas, gas hydrates) in deeper sediments. Detailed analysis of gas compositions aids in the assessment of marine ecosystem vitality and the monitoring of pollution impacts, thereby guiding sustainable resource management strategies. Additionally, investigations into sedimentary gas unveil enigmatic microbial life forms with promising applications in biotechnology and medicine. This multidisciplinary field significantly advances our comprehension of Earth's temporal trajectory and underscores the imperative for actions conducive to a sustainable future. In this special issue of Geo-Marine Letters (GML), we welcome papers of different topics, including but not limited to: (1) the upward path of gas: from the subsurface through the ocean to the atmosphere, (2) gas reservoirs, active seafloor gas emissions and tectonics around the world, (3) seafloor gas hydrates in the oceans, (4) mud volcanoes: structure, plumbing, chemistry and mechanisms triggering activity, (5) biogeochemical processes and chemosynthetic organisms at hydrocarbon seeps, and (6) the complex interplay of gas emissions in marine sedimentary basins in polar regions, Arctic and Antarctica.