Lost Cities 1.18-5.1.0
Split this out of Issue #422 so it's not grouped with those other issues. I did a little more testing and it appears that basements generate fine for buildings where cities generate on land. It's cities that generate over ocean where the basements stop at water level.
Generated over ocean:



Generated over land:


Tested various locations on land and basements generate down to Y54, so below water level.