I see your question has generated some comments about detecting on federally managed beaches. And no doubt, if you asked enough federal rangers, they'd look up in their books, and get back to you with a "no" (afterall, you asked, they're going to dig in their books to find your answer).
Here's a true story of a guy who hunted a federal beach here in CA 15 or so years ago: The fellow was a newbie to detecting, and was trying to decide where to detect. So .... doh ... he decides he'd try the beach near him. So he goes there, and is simply amazed at the staggering amounts of coins in the dry sand. Coin counts of 200 to 300 in a single hunt, and some rings now and then too. He's over-joyed at his stroke of luck at finding this red hot beach. He simply can not believe the long-time locals hadn't hit this beach (as he was aware that there were hobbyists in his area). He posted his finds (but not his beach location) on a forum. I saw that he was in my state, and only a few hours from me. We traded some emails, and I got his confidence up enough to reveal to me where his honey-spot was. When he told me the name of the beach, I told him that that is a federal beach, and that I'd heard that detecting is not allowed (although I'd never personally been there, as it's too far from me). He emailed back that he simply couldn't believe that it "wasn't allowed". He said that for the past several weeks, several times per week, he had simply gone there and helped himself, in broad view of anyone and everyone. Yup, right in front of manned lifeguard towers, all around the parking lots where rangers come & go, etc... No one had even said "boo" to him. So he was confident that I was mistaken (because .... certainly .... someone would have said something by then, right?) I think he eventually looked into the matter, and perhaps did see the vebage I was talking about. It was then that he realized why he'd been doing so good: other locals just assumed you couldn't do it, so the beach was practically virgin. But the other part of him felt like simply continuing, since it was OBVIOUS that in "actual practice", no one cared (perhaps no one's ever asked enough questions there? I dunno).