attention along the coast in san mateo county. it was a tsunami test. but as we learned it didn't reach everybody it was suppose to. [loud noises] >> reporter: these sirens sounded just after 10:00 this morning, heard from pacifica, down to half moon bay, a test of the tsunami system. one man plugged in his ear plugs, and surfers stayed near the water, waiting for the next wave. some didn't know what happened. >> i figured it was a shark thing, just because -- i don't know, i have no idea. >> reporter: but people along the coast believe tsunamis do pose a threat. they want a solid warning system. >> there is potential, it could happen, you can't put anything past mother nature. >> the sirens themselves will last for approximately one to three minutes. >> reporter: this morning's test was done by the san mateo county office of emergency services. over the past four years, they have installed new sirens that