concrete, habitat, ocean, colonization, oceanic, concrete submarine habitat, #ConcreteSubmarineHabitat
#ConcreteSubmarineHabitat
http://concretesubmarine.activeboard.com/t56239662/oceanic-concrete-sphere-habitat/
http://concretesubmarine.activeboard.com/t43942461/the-captain-nemo-float-out-seasteading/