I grew up in Southern California and have been to most every beach from Santa Barbara to San Diego. To put things into perspective, when I was in elementary school, our YMCA camp took us to different beaches every week. There were usually lifeguards, but we were generally unsupervised by today's standards. I was out in the sun all day and learned to be a strong swimmer. Yes, I've been knocked around a bit, but it was good for me to learn and experience. I still live on the water, on a sailboat, and am raising two young children around the ocean. It's good to be cautious, but, if your kids are good swimmers, I would set limits, supervise, and then try not to pass on your fears to them. The ocean is an incredible place. Enjoy and welcome to CA!