Chosen design to develop: 

I decided to develop Draft Mod2 because I really want to have a half submerged construction underwater. It is quite unique. I also decided to have a kind of 1 elevator tube from the ground building to the floating sphere. The base/lowest level of the sphere is solid the other two levels can be used.

Measurements: 0.5m thickness of each floor, 0.2m thick wall, 3m high for each floor, the Sphere has radius 10m.

I made the ground plain and ocean for the 2 constructions to be placed.