To your point of this technique not being new: the mulberry harbors the allies built following the d-day invasion of operation overlord made use of prefabricat

To your point of this technique not being new: the mulberry harbors the allies built following the d-day invasion of operation overlord made use of prefabricated sections code named phoenix, that were towed into place and then sunk to form the structure of the harbor. They were so named, I think, because after being built they were sunk off the coast of England before being refloated in preparation of the operation, i.e. like the phoenix the rose, or something poetic like that. If you're ever in or around Normandy I highly recommend a visit to the beaches. They're much bigger than I had imagined, and it really hit home then what a massive operation it was. Anyway – no, the technique is not new.