They did a great job of making the location look real. I know, because I was there.
I tried several searches but nothing showed up.
The front page of IMDB didn't seem to have a reference to it.
But I might have missed it. I figure someone might have read it somewhere.
The pilot episode was filmed mostly in Ohau, Hawaii, while some scenes, as well as every episode therafter, was filmed at the Malibu Creek State Park located off 1925 Las Virgenes Road, Calabasas, California.
It is the same setting where they filmed the M*A*S*H* TV series Army camp as well as the movie version of it. Many Hollywood movies and TV shows were filmed at Malibu Creek State Part from 1968's Planet of the Apes to many Beach Party films of the 1960s, and other films too numerous to list here.
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...I was there.
Thank you for your service to our nation!