I saw the procedure once, they make a case, pump out the water, then pour the concrete. It's this what you mean? But its a complete other think doing such a big structure... one has to consider the pressure of all that water also. What material would be used to make such a huge underwater building first to afterwards do it in concrete?

I saw the procedure once, they make a case, pump out the water, then pour the concrete. It's this what you mean?