Open year-round, the swim center heats up in summer, when it seems everyone in the East Bay -- particularly refugees from the fog belt -- arrives for a day of poolside fun. Part of the 66-acre Refugio Valley Park, the swim center has two gigantic pools: one for laps and diving, and another extensive wading pool with a Fantasy-Islandesque fountain and a beach-like graduated bottom, which means baby can play safely while older kids and parents enjoy the water. Locker rooms provide ample showering amenities, and the pools are surrounded by grassy space perfect for sun tanning or picnics. For those who crave structure, the center offers group and individual swim lessons, water-exercise classes, lap swimming, lifeguard and water safety instructor training, and diving classes, as well as opportunities to swim with various teams. Hours and fees change by season.