On this "When"sday I go back to just outside of San Diego. The place is called the Devil's Punchbowl. Amazing hike not too far away, and beautiful, but the water was cold! Lots of local kids came here in the summer to swim in this fun place, and jump off the rocks!
Fun Fact: Even in the dead heat of summer the water can still be as cold as sixty degrees Fahrenheit.
Side Tip: Go during the spring, summer may be too hot to go, and sometimes it will be closed because of the danger. Pack snacks and water, it can take a while to get there and back, but it's totally worth it!