As traffic on the humpback highway ramps up along the east coast of Australia, a baleen whale on the other side of the Pacific has attracted attention for almost swallowing a sea lion.

Wildlife photographer Chase Dekker snapped the encounter during an anchovy feeding frenzy in California's Monterey Bay.

The sea lion appears to have got caught on the wrong end of the food chain and by the look on its face was as shocked to find itself between the humpback's jaws as the Californian photographer was to capture the moment.

"The whale lunged out of the water with that big mouth and this time I guess the sea lion didn't move out of the way quickly enough — it was a little distracted I guess," Mr Dekker said.

Mr Dekker, a wildlife and conservation photographer, said it was common for humpback whales and sea lions to feed together during the anchovy season in the northern hemisphere from spring through to autumn.

Californian wildlife and conservation photographer Chase Dekker is following the humpback whales to Fiji and eventually Australia. ( Supplied: Chase Dekker )

"As the whales come up to feed at the surface usually the sea lions dart out of the way — but not this one," Mr Dekker said.

Despite appearances, the photographer said he was 100 per cent confident the sea lion survived the ordeal.

"Generally they close their mouths immediately to trap fish," Mr Dekker said.

"This one actually kept its mouth open for about 10 to 15 seconds and kept it open as it sunk beneath the water.

"Whether the sea lion jumped out on the surface on the other side where we couldn't see, or swam out beneath the water, I'm 100 per cent confident the sea lion escaped.

"I think it was completely unharmed because the whale never closed its mouth, so there wouldn't have been any pressure."

Chase Dekker captured this spectacular image during a massive feeding frenzy. ( Supplied: Chase Dekker )

Director of the Oceania Project at Southern Cross University agreed the humpback whale would have done all it could to remove the sea lion before swallowing.

"What whales do when they're eating anchovies is use their tongue to push the fish towards the top of their mouth to push water out," Dr Wally Franklin said.

"If there was something much larger, like a seal, I'm certain the whale would dislodge that before it swallowed.

"It was probably an accidental encounter."

However Dr Franklin, who has been studying humpback whales in Hervey Bay for 30 years, has never seen anything like it.

But he said he wouldn't rule out the possibility that an Australian fur seal could find itself in a similar predicament.

"When other mammals are feeding in and around where whales are feeding that is always going to be a possibility," he said.

Mr Dekker is following the humpbacks to Fiji and Tonga and hopes to photograph Australia's humpback highway next year.