>>1752354This idea was reintroduced in some regard after Hurricane Sandy, with the idea of a flood gate system created to protect New York Harbor, with the barrier from Sandy Hook in NJ to Breezy Point in the Rockaways.
At this point the land inside this system could be reclaimed, theoretically, but yeah, it's too expensive to ever happen, at least not this century.
https://en.wikipedia.org/wiki/New_York_Harbor_Storm-Surge_Barrier 