campgrounds with hiking near bodies of water?

hi guys, new here. looking to get into the outdoors more with camping/hiking however i am looking for any areas that i can reserve a campsite within the next few weeks/months that is near any decent sized body of water like the ocean or lakes or whatever. i have been google searching and i am overwhelmed by the amount of information to go through. i will have a decent sized camping/hiking group of around 4-10 people over 1 or 2 days (weekend camping/hiking), the group will be a mixed bag of hiking xp/levels from beginner to expert. i guess this would be too much to ask but is there anything relatively close to long beach ca? thanks in advance!