This is Lagoon Point, Whidbey Island, Washington, a truly artificial creation, at least most of it. Virtually all of the lagoon and beach (the stuff in the photo shown sticking out into the blue of Puget Sound) was either 'sluiced' from the cliffs above or dredged up from the waters below during the late 1950s. Sluicing [pronounced SLOOSing] is a mining technique whereby water is shot from water canons into the earth and the resulting slurry is sluiced away (in this case, right into the marsh below). Sluicing of the cliffs and dredging of the marsh resulted in the dry land, 'inland' waterways and beach that we know today as Lagoon Point. The extensive amount of intrusion into Puget Sound caused by this development would not be legal today due to environmental laws passed during the 1960s. But it was probably a lot of fun to watch at the time!
(Thanks to my brother-in-law Stuart for this aerial photo).