The Aquatic Park (Beach St. and Hyde St.) beach sits right in the middle of Touristville, San Francisco (Fisherman’s Wharf [1], that is). Of course this makes Aquatic Park incredibly convenient for visitors who want to grab a picnic on the Wharf to enjoy down on the beach. To be honest, the coolest part of Aquatic Park is its history rather than its current presence.
The park was built in the late 1930s as a bathhouse catering to wealthy San Franciscans, and today one of the main attractions of Aquatic Park remains swimming: triathletes and hard-core swimmers brave the frigid waters to swim for miles in the protected cove. More sedate visitors prefer to find a seat and enjoy a cup of coffee, a newspaper, and some people-watching.
Links:
[1] http://www.moon.com/destinations/california/san-francisco-and-the-bay-area/sights/north-beach-and-fisherman-s-wharf/fisherman-s-wharf