There are many areas of offshore basalt around the world which may be suitable for carbon dioxide (CO₂) storage.  Future projects at these sites may act as storage for carbon dioxide that is captured onshore, relying on vessels or pipelines to transport the CO₂ to the storage location.  Alternately, a fully offshore Negative Emissions Technology (NET) system could be created which captures carbon dioxide at or nearby to its selected storage site; this both reduces transport costs and makes it possible to use plentiful renewable energy resources that are far away from grid-connected energy markets.  However, many of these sites are located further from shore and in deeper water than currently existing offshore carbon capture and storage (CCS) and offshore wind projects.  Such sites may also experience severe weather conditions more frequently.  This research assesses the implications of these novel contexts on vessel performance when using ‘conventional’ vessel designs for two applications: transporting CO₂ from major ports to ocean basalt storage locations, and providing maintenance to an offshore-wind-powered NET system. A GIS assessment is employed to identify potential basalt sequestration locations globally. Distances from these locations to major ports and to viable areas for wind farm development are then computed, and weather conditions at sample locations are estimated using global reanalysis data. For the first application, transportation costs are computed using techno-economic models for vessel transportation. For the second application, the open-source offshore maintenance tool WOMBAT (Windfarm Operations and Maintenance cost-Benefit Analysis Tool) is modified to analyze the effectiveness of maintenance support to offshore wind farms with integrated direct air capture devices that are situated within close proximity to basalt storage sites.