Lake Gregory Regional Park, Crestline

If you wanted to skip a stone from one end of Lake Gregory to another, you'd have to have quite an arm. Nestled in the San Bernadino Mountains, the lake sprawls across 84 acres—that's 60 football fields—which means it's vast enough for every type of aquatic entertainment. An inflatable play structure dubbed Splash Island floats on its surface, welcoming youngsters to swim, climb, and zoom down a waterslide. Fishermen tour the lake to bait its trophy-sized trout, which are stocked twice monthly. Other visitors explore the waves on rental kayaks, stand-up paddle boards, and aqua cycles, which are much more useful than a regular bike wearing water wings.