Humpback whale turns toward sea after almost landing on the beach.

A woman jogging on the beach in Pacifica, Calif., was astonished to see a humpback whale swimming straight toward her through the surf, seemingly intent on beaching itself.

"Whoa, stay back, buddy!," Roberta Gamble said to the whale, while videotaping the rare encounter on Monday morning.

Humpback whales were feeding beyond the surf zone, but this whale had chased a school of anchovies almost onto the shore. It opens wide to gulp the bait fish, directly in front of Gamble, about 5 seconds into the video.

"Oh dear," she says in the short clip, which on Thursday began circulating on whale-themed Facebook pages.

"Although humpbacks have at times been observed lunge-feeding just outside the surf zone, it is extraordinarily rare to catch one with its belly actually on the sand," whale researcher Alisa Schulman-Janiger posted on the public group, Cetal Fauna. "I’ve witnessed humpbacks feeding close to shore here, but always just outside the surf – never this close!"


Humpback whale opens wide for anchovies as it almost comes ashore.

Bottlenose dolphins, humpback dolphins and killer whales sometimes engage in what's called strand feeding, where they briefly beach themselves during predation events.

This behavior has not been documented among humpback whales, but the whale in Gamble’s video definitely touched its belly to sand in a determined effort to catch the fleeing anchovies, which are what attracted so many voracious gulls.

RELATED: Humpback whale surprises dog on beach

It's not clear, however, if this was intentional strand feeding, or if this whale simply was chasing prey as far as it could before it realized it had run out of liquid real estate.

Gamble told GrindTV that the encounter occurred on a remote stretch of beach a half-mile from the nearest parking, south of Pacific Pier, and that only a few other people witnessed the event.

"I was down there for at least 20 or 30 minutes and it was still going on when I left," she said of the near-shore feeding. "It looked like just the one that close, but there were others not too far away."

Gamble explained that the whale she videotaped “methodically would swim out then in along the coast, and circle around again.”

Last month off Pacifica, a group of surfers were riding waves when feeding humpbacks crashed the lineup, in what was also considered a rare event.

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