When we enter the ocean, we enter the wilderness. I often feel I should ask permission before I paddle or swim out, because humans are, after all, mere visitors in this vast, mysterious realm.

Among its mysteries are the behaviors and motivations of sharks, which some surfers, including myself, have seen in the waves.

“Sharks surf waves just like porpoises — they ride the shoulder and usually stay out in front of the white water,” John Clark, author of “Hawaiian Surfing: Traditions from the Past,” told me in an email.

Once, when he was surfing at Cliffs off Diamond Head, “I was paddling out and a guy took off going left, coming toward me,” Clark said. “Then I saw a shark about six feet long riding the wave out in front of him. The shark stayed in the shoulder and passed between me and the surfer as the wave went by.”

Another time at Cliffs, Clark watched a shark surfing on a wave that was breaking right, toward Black Point. “This time, though, the shark had the wave to itself.”

I asked Carl Meyer, a scientist at the Hawai‘i Institute of Marine Biology who studies sharks, whether the predators enjoy riding waves.

Meyer replied that many species of sharks are present in surf zones, which often include good habitats for finding and trapping prey. “Consequently it is not unusual to sight sharks in the face of waves, swimming parallel to, or with the breaking wave.”

But, he added, the idea of sharks having fun and catching waves is “too anthropomorphic.”

Just as seabirds soar on air currents, Clark explained, sharks coast in waves, but this is natural and reflexive — not deliberate — behavior. “Coasting saves energy, (which) means you do not have to eat as much to survive, grow and reproduce.”

I hope this means that sharks may be less likely to bite surfers they encounter while they’re saving energy by coasting on waves.

Not that I’d recommend testing it.

NEIL MCHENRY, who used to live and surf regularly at Tonggs, a break that lies between Cliffs and Waikiki, emailed me a recollection of a shark sighting in the waves.

“There was a rumor that a 14-foot shark named Sam patrolled Ricebowls and Zeros (deepwater waves that break outside of Tonggs on big swells). It’s 1963 and the ocean is just like glass, no ripples, 8 a.m. in the morning, the sun is out. Randy Steiner and I are 17 years old and we are out at Zeros. (It’s) a solid 12 feet,” McHenry said.

“We’re in between sets. Randy is two feet away from me with his back to the waves, his feet dangling in the water, sitting on his 11-foot Wardy surfboard.

“Reflecting on the beauty of the water, I see a small ripple the size of a dinner plate appearing next to Randy. I thought, what a strange little boil. The boil slowly opened up without a sound and grew and grew. Slowly in the center of the boil a fin slides up and out!!! A HUGE FIN … A Monster Fin … .

“IT’S SAM … and then his large back, like a gray submarine, emerged by Randy — (who’s) not even aware of it — and it seemed to take forever, (until) finally Sam’s two-foot-tall tail fin came up and disappeared into the deep blue water, leaving only a small ripple in the glassy sea.”

McHenry alerted Steiner and they went in to shore.

I did the same when, one gray, drizzly day with big waves in 1969, I saw a huge shark suspended in the face of an outside wave at Tonggs like a trophy mounted on a glass wall.

Its mouth curved in a semblance of a smile, the shark looked relaxed — coasting, maybe. Nevertheless, the sight filled me with terror; I warned the other surfers and went in.

“Oh, that’s just Sam the nurse shark,” said another member of the Tonggs Gang. “He’s not aggressive.”

Maybe it wasn’t Sam who, later that year, chased Tomi Winkler and Willie Hawthorne all the way to shore. A photographer snapped them paddling frantically with a 2-foot-tall, black fin following close behind.

Or maybe it was.

“In the Lineup” features Hawaii’s oceangoers and their regular hangouts, from the beach to the deep blue sea. Reach Mindy Pennybacker at mpennybacker@staradvertiser.com or call 529-4772.