Existing supertankers can displace in the hundreds of thousands of tons. New, they cost under $100M. Scrap, much less. They are not bothered much by weather, i

Existing supertankers can displace in the hundreds of thousands of tons. New, they cost under $100M. Scrap, much less. They are not bothered much by weather, in normal operation. With that much weight hanging well below the surface, they would be very stable. (Racked together side by side, moreso.) Think of it as a very long oil platform. Those endure any weather with no difficulty. No need for anything attached to the bottom except anchor chains. When planning ocean operation, make sure almost everything is at or well above the surface, and everything complicated (motor/generator, winch, power conversion) is well protected from exposure. Ocean deployments that expose expensive stuff to wave action or put it underwater fail, reliably. (Expect tidal generation that puts generators underwater to fail spectacularly.) Offshore wind has the nacelle well encapsulated and everything that moves far above the waves. Nothing is underwater except the pilings, the end of the support post, and a wire.