This bug was fixed in Patch 1.84.171
I loaded a lot in Evergreen Harbor in build mode and now it looks like it’s underwater. There’s no ground or streets.
The bug only appears if you load the game directly to build mode from the map and only if you never visited the neighborhood before in live mode.
Affected are new games and old ones that were never played in the neighborhoods.
Load any lot in each neighborhood in Live Mode. You can either do this by loading into a household or by visiting each neighborhood with a Sim.
After doing that, build mode should also look normal again.