In my opinion, and again, this remains somewhere around an idea / talking point / suggestion, such “beasts” might better (best?) be represented by an OSM way. A node was a “beginning seed idea” and “as of now” (we can and should keep talking about this) it seems to be more widely acknowledged (in this thread) that a way can characterize this much better than a single, simple node could. (We have also discussed a newly-coined relation flavor, but its type=* remains unspecified, open to suggestions).
Clearly, a node is “not enough,” and “beast” (multi)polygons we’re seeing are both overwhelming to our database, sensibilities and correctness. So, a way, as a “line string” that follows the centerline of such large objects seems a suitable compromise, so much so it might prove a workable solution in many or all cases.
The relation idea I suggested earlier might work also, but then we’d be back to “what are its components?” That’s fine, though there is a risk of these, too, becoming “beasts,” but a potential relation solution has the benefit it can have a mix nodes and ways. I think if proper role tags are established to denote what we mean by any nodes and ways in such a relation type (similar to a “label” role tag in a type=boundary relation), this could prove to be a quite versatile solution. For example, it could work with more than “large seas,” it could work for mountain ranges and other geographically large items where rendering now proves difficult.
But for now, let’s stick with (the idea, talking point, suggestion of) a simple way, as I think @ZeLonewolf might be refining something (beyond his initial Proposal) which would include a proposed method of defining a single OSM way to do this. I await seeing something from him on that (but he is a busy man!)
Good dialog here, good progress on brainstorming here!