(Monterey, CA)  --  A tsunami advisory that went into effect for the West Coast Saturday has expired but officials in some places are still urging caution in case lingering strong currents remain.  The tsunami advisory came after an undersea volcano erupted near the South Pacific island of Tonga, triggering a huge earthquake.  Despite the tsunami advisory, surfers and swimmers still flocked to beaches over the weekend, keeping first responders busy.  Hundreds showed up to San Francisco's Ocean Beach to get a first hand look at the waves.  About 25 ended up in need of rescue.