Open Question: Are there any secluded swimming holes or lakes in Southern CA (Orange County specifically)?

I am looking for a quite and secluded swimming hole, lake, or whatever where you can just hang out. I don't want to have to deal with a lot people (or any people really) and I would prefer to not have to pay an admission fee just to go hang out for a couple of hours. Does anyone know of any good spots in Southern CA (Orange County)?

Source:
http://answers.yahoo.com/question/index?qid=20110630170101AAjigwC

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