Surfers and ocean swimmers are being cautioned that there have been several sightings of great white sharks near the San Francisco Peninsula — and this is the typical time of year that sharks show up in the area from their migration to the deep ocean.

Multiple pilots have reported seeing the large marine beasts from the air off the San Mateo County coast, as ABC 7 reports. And as NBC Bay Area reports, four sharks were seen from the air in recent days about 40 yards from the beach near the Ritz Carlton Half Moon Bay.

Sharks tend to come to shallow water in search of warmth, because they are sensitive to temperature, experts say. And as the Chronicle explains, great whites come to feed around the Farallon Islands in late summer and fall, after making annual trips out to deeper waters.

A separate great white sighting happened last month off the Sonoma coast, near Bodega Bay, which halted some county sheriff's deputies from doing some water training.

Back in March a jet skier at Mavericks shooed a shark away from a group of surfers, and brought the surfers back to shore before anyone could get bitten.

There are roughly 65 shark attacks worldwide each year, and many of those happen to surfers. As Swim Outlet explains, shark experts tend to believe that most shark attacks on humans are cases of mistaken identity — people in wetsuits paddling on surfboards bear a resemblance, from below, to swimming seals, which are sharks' prey of choice.

If you spot any sharks, you're encouraged to contact local law enforcement — and get the hell out of the water.

Related: Jet Skier Saves Mavericks Surfers From Enormous Great White Shark