Four diving buddies seeking a close-up look at the sea life off the California coast got way too close for comfort, with one nearly becoming part of the food chain.

“That was my once-in-a-lifetime whale encounter,” Shawn Stamback told The Tribune of San Luis Obispo, Calif.

Stamback and his friends encountered a pod of feeding whales last Saturday near Souza Rock about 2 miles off the coast of Avila Beach. During a break, Stamback and one friend jumped off the dive boat with GoPro cameras mounted on their heads to do some snorkeling.

“Before I knew it, a big boil of bait fish started shooting up in my face,” Stamback told his local newspaper. “As soon as that happened, I knew exactly what was going on. I knew there was a predator chasing those fish.”

However, he added, “I had no idea there was a freaking freight train behind those fishies. That really blew my mind.”

Click play to watch the close encounter. (Warning: The audio contains several expletives.)

Before he could react, two humpback whales rose in unison out of the water just a few feet from Stamback. The whales, mouths agape, gulped mouthfuls of fish and sank back beneath the waves.

“You see pictures, representations of how big a humpback whale is, compared to a bus, to a jet. When you see one in person that close, they are giant and it blew my mind how big they are,” Stamback told NBC Bay Area News.

Stamback acknowledges that what he hopes is a once-in-a-lifetime encounter could have been disastrous. He could have been swallowed or the boat could have capsized.

The two divers hurried back to the boat and called it a day.

“We pretty much figured that we used up all our luck for the day, so why push it?” Stamback told the Tribune.

The video shot from both Stamback’s GoPro camera and another from the deck of the dive boat has been a viral sensation, with more than 4.6 million views as of Wednesday. It was posted Saturday on YouTube.

Monica DeAngelis, a mammal expert with the National Marine Fisheries Service, said she could not say based on the video whether the divers were violating the Marine Mammal Protection Act, which bans harassment or the altering of mammal behavior. NOAA whale-watching guidelines recommend that boaters stay at least 100 yards from whales.

“They certainly are lucky no one got hurt,” DeAngelis said.