Seacliff State Beach is good for swimming, but watch out for the riptides. There are lifeguards on duty during peak season. There's a pier for fishing, and a sunken ship that has been converted into an arcade . . . Lighthouse Field State beach is not a beach for swimming. As for surfing, it is good, but only the more experience ones should head out.
Most people watch the surfers from atop the cliffs overlooking the rocky shoreline.
Capitola City Beach is also good for swimming, as the tide is gentle. The pier offers decent fishing, and the nearby shops and restaurants make it a convenient spot to visit. The parking, however is scarce, and not for free. Twin Lakes State Beach offers warmer water for swimming, as well as public restroom facilities and showers. Lifeguards are on duty during peak season.