HALF MOON BAY, Calif. (KGO) -- Some beaches along Half Moon Bay have posted an advisory for people planning to go into the water. It reads: "Shark Sighted. Use Caution."
A group of guys from the East Bay launched into the waters off Half Moon Bay just before 8 a.m. on Friday for an early morning fishing trip.
They didn't know about the 24-hour shark advisory, which expires around 5 p.m. on Friday. They say the warning is something to think about, but not enough to cancel their plans.
"We will be on our boat, we will be safe. Sharks are common, so yeah, we won't be jumping in the water," says Dublin resident Allen Nguyen, who is part of the fishing trip.
"Definitely, it is concerning. But it's a part of nature. We just have to risk," says Ryan Assadi, who also lives in Dublin.
On Thursday afternoon, the San Mateo County Sheriff's Department issued a tweet warning that multiple pilots flying over the San Mateo County coast spotted several great white sharks in the water. "If visiting the area, please use caution," the tweet read.
The sharks were spotted between the Ritz Carlton and Pillar Point.
Great white sharks aren't just limited to San Mateo County, one was spotted off the coast of Sonoma County last month.
"Got to remember that the ocean is a live, dynamic environment. They're always out there. That's their home," explains Officer Jeff Wadkins, with California State Parks.
Officer Wadkins says it is not unusual to see great whites swimming off the coast of California. He says sharks don't automatically pose a threat. The advisory is just to keep the public informed and safe.
He adds, "Sharks have been aggressive in the past, but it's very, very rare. And we have never seen any attack in Half Moon Bay or the San Mateo Coast."
Wadkins says park rangers are monitoring the coast with other local agencies, and that all of Half Moon Bay's beaches will be fully staffed with life guards throughout the weekend.
If you see a great white report it to local law enforcement.
See more stories on sharks.