This is the swamp biome with the floor removed/replaced.
Marked in red are area blocked by invisible entities. Could it be a flup spawner?
Has there been any update that have the potential to cause white whales stop spawning? Since this morning I haven't see any of those. All 15 + whales that I've killed today are blue whales.
Steps to Reproduce
Get to a swamp. Kill all the flups, burn and remove everything. Then try building random stuff all over the place. There will be empty stop that doesn't allow for building placement.
This issue has not been confirmed by a developer yet.