The treasure stored in Mark Cunningham’s garage has been carefully sorted in boxes, buckets and empty plastic snack containers. But if you didn’t know his grand plan, you would think the famous bodysurfer was preparing for a bulky-trash pickup day.

There are hundreds of items, all plucked from the ocean. Most have a crusty patina of coral.

This is what a lifetime at the beach will produce, says Cunningham, a retired Hono­lulu City and County lifeguard and the state’s pre-eminent bodysurfer. Then he cheerfully adds, "Yeah, I’ve got a problem."

There are surfboard fins by the hundreds, sunglasses of every style, scuba masks, swim fins, credit cards, hotel room keys, a Hawaii driver’s license that once belonged to a woman named Christy, watches, car keys, green-tinted coins, a splash guard from a Hawaiian outrigger canoe and dozens of used toothbrushes.

Cunningham can’t figure out why anyone would take a toothbrush to the beach. But the real question is, Why does he have them? Why does he have any of this?

It’s simple, he says. It’s art.

For years he’s been known for his bodysurfing skills, fearlessly riding big waves at the treacherous Banzai Pipeline. But Cunningham has a passion for art that he’ll put on display Friday when "Lost & Found: Reef Relics" opens at Muu­muu Heaven in Kai­lua.

Cunningham found the items in his collection while snorkeling at Oahu’s beaches for nearly 40 years. He went to the most popular surf breaks, places where the waves were powerful enough to snap boards, and explored their depths when the waters were calm.

He never thought of his collection as junk. Instead, he always saw beauty.

"I like this detritus from the impact zone," says the 59-year-old Cunningham. "We all see guys ripping and riding, and we go ‘ooh’ and ‘ahh’ at a wipeout. Well, this is the remains of the wipeout."

Surfboard fins are the largest part of his collection. To Cunningham they’re as much a work of art as they are vital to a surfboard.

"They represent surfing to me," he says. "To me it’s sculpture, and I wanted to share it rather than let it sit at the bottom of the ocean, forgotten. That didn’t seem quite right to me."

The garage is not the only place you’ll find fins in the Wai­alae Nui home Cunningham shares with his girlfriend, artist Katye Killebrew. No matter where you look, you’ll see fins.

They sit on shelves and countertops like sharks gliding through a room. They line the top edges of window and door trim. Others are mounted on weathered driftwood that Cunningham found at the beach.

They’re even printed on his shirt.

But one creation stands out: a galvanized tub, about 2 feet across, that’s been packed with old fins. It’s called "Fin Anemone."

Cunningham, who put it together several years ago with Killebrew, says this is where his collector’s obsession took its first artistic turn. At the urging of a friend in the surf industry, the distinctive piece was shown in a New York art exhibit in 2012.

"We took it all apart, emptied the bucket and shipped it box by box and reassembled it in New York," Cunningham says. "There are 850 fins. When Katye and I reassembled this, we counted as we put them back in there."

Most of Cunningham’s fins were underwater so long that they have significant coral growth — wartlike nobs on some, delicate filigree on others. A few are so completely encased with coral, they resemble pieces of freshly battered fish ready for a deep-fryer.

Each of his fins is a beautiful mystery. The bodysurfer holds up a thick, large fin that was wet-sanded by the shifting tides. You can see the layers of fiberglass cloth that were used to create it. Cunningham calls fins like this "witches’ hats" because they are curved and pointy.

"Who shaped this?" he says. "Whose board was this on? Did someone lose it on his first wave? Did he run over someone? And how long has it been in the water?"

Cunningham’s obsession started soon after he became a lifeguard in 1976. One day a tourist lost a gold ring in front of his lifeguard tower at Ala Moana Beach. Beachgoers searched for hours without success. Later, after everyone had left and Cunningham’s shift was over, he put on a mask and snorkel and went looking.

He found the ring, of course.

Initially, Cunningham saw snorkeling as a lucrative hobby. He discovered he could easily find swim fins on the bottom and sell them back to the bodysurfers who lost them. But as he prowled the bottom, he started finding beautiful surfboard fins. Whenever he snorkeled, he would look for them.

Cunningham retired from lifeguarding in 2005, and the free time he gained allowed him to snorkel more with Killebrew. He still bodysurfs regularly, but the snorkeling gives him just as much pleasure as a barrelling wave.

Bodysurfers ride inside the wave, and Cunningham thinks that may be the reason he’s driven to look below the surface of the ocean.

"It’s the other half of the picture," he says. "It’s so beautiful in the underwater world, and then, to find these treasures — it’s kind of like an Easter egg hunt."