This morning's prompt is 'pea pod'.

(I don't know why I'm captioning the sketch, now... 8-P)

So I'm thinking about my clunky million square kilometer blobs for no good reason and the edges of the quads are really curves so my approximation just got even more complicated; adjacent rows of 13 and 18 blobs have 13*18  or 234 segments, each preceding area having 18 segments on the bottom, each, and each next row area having 13 segments on top. Each area is actually a polygon which we can imagine subdividing into a triangle fan around the center, doing a drunkards walk to find land or sea areas, then randomize the border vertices based on the centers' height above or below sea level.

We can cut down on edge segments by only considering any shared quad corners in the top and bottom edges; we may consider many possible points but only keep track of corners.