From what I have heard, Laguna Beach Lifeguards are deputized by the Sherrifs dept. to write citations if you are caught diving w/o a snorkle or a buddy. Although they do not tell you where you have to wear them, or what the definition of a snorkle is, they will ask you either before you go in the water or tell you you need one when you exit the water. A buddy of mine once used a foot long piece of garden hose and won an argument about wether it was a snorkle or not. Another was told that his snorkle needed to be on his mask, it does not.
If you go in the water and leave before they show up, you have no problems. In the summer I carry a snorkle in a pocket. In the winter there are no lifeguards around, so I leave it in my car or at home.
If you dont have one and they hassle you about a snorkle when you come out of the water, tell them you lost it in the water and they are pretty much cool with that.
The biggest thing they are concerned about is wether you have a buddy or not. In the past (before I started diving w/DIR buddies) I have come up without a buddy and been confronted by lifeguards asking, understandably, where my buddy was. I told them that our dive plan was that if we became separated, we would meet on the beach w/i 10 minutes of each other. It worked because it was basically our dive plan anyway and we waved to the lifeguard as we headed up the stairs.
The moral of the story? Buy a cheap folding snorkle if you plan on diving in Laguna in the summertime. The more crowded the beach is, the more of a hard-on they have for divers. More people to pay attention to in the water, and a lot of the divers have attitudes with them to begin with and it just makes thier jobs a little harder. Be cool and have yourself covered, or dive Laguna in the winter.
Dive safe,
dive often.
Robert