this discussion are interesting! In additionally, for more detail tagging information about the type of landuse either it's an island, coastline  or wetland you can reach the wiki map features  (https://wiki.openstreetmap.org/wiki/Tag:place%3Disland) and compare to (https://wiki.openstreetmap.org/wiki/Coastline) and (https://wiki.openstreetmap.org/wiki/Tag:natural%3Dwetland)

May this help you identify the most suitable tagging for this issue. Thank you and happy mapping