It could be guessed that an ONAN had struck the ground somewhere nearby, several decades ago. Seed-packed siwis had slithered out of it, roaming about, mapping elevations and soil moisture, comparing notes over a mesh network. The collective had noticed the break in the slope leading down to the sea. Following a program drilled into it by some coder up on the ring, it had decided that the coastline might be stabilized here by planting some seeds that would grow up into tough, low, scrubby vegetation. And so it had all come to pass. Siwis that happened to wander away from the beach had found the flat ground beyond the rim and planted it with different species that would thrive in a wet environment. The vegetation had created a bit of a natural dam, holding back water coming down out of the mountains above them. One day it might be a lake, but for now it was a black bog, squishy and knee-deep and screened with grasses and reeds that favored that sort of ground.