An easy manufacturing method would be to 3d print in plastic a double walled shell, with fill holes for concrete, and mounting chanels for motors. Plastic "lining" would provide salt water protection for the concrete.

[–] aim_at_me@lemmy.nz 2 points 1 day ago* (last edited 1 day ago) (1 children)

We have seawater resistant concrete. We don't need to plastic line it. It's the turbine that'll require the most maintenance.

[–] rhombus@sh.itjust.works 1 points 16 hours ago

Depends if the spheres require any steel reinforcement; the salt penetrates the concrete and absolutely wrecks rebar. Though I imagine spheres at depth (not to mention with a partial vacuum) can function like an arch and support themselves with compression, which concrete excels at.