The coastline glob adapter currently uses a flood-fill to create ocean and land based on OSM data. However, due to inaccuracies, this can lead to points being flood-filled more than once, or wrongly, which has a huge performance impact.

Instead of using flood-fill, this should rather create polygon(s) where the ocean would be, and directly fill that. All coastlines that have shared nodes should be joined to a single line for this process.