It’s not the cold, dark water that concerns me. Or the ripping current, speeding boats, or half-ton tiger sharks. It’s the weight—the 50 or so pounds of lead that Paul Burton straps on to sink himself to the river bottom, where he will spike his way upcurrent with the aid of a screwdriver or maybe a shard of found whale rib, groping blindly through the Miocene muck for a hand-sized wedge of fossilized gold.

It isn’t that his hobby of diving Lowcountry tidewaters in zero visibility for giant shark’s teeth seems crazy, or that his mentor in the sport of fossil diving actually died at the bottom of another river eight years ago, or even that Paul is supposed to take me cobia fishing in about a month. It’s the sheer density of his commitment that rattles me.

“The biggest tactical error is being underweighted,” he says, nestling some extra lead ingots in the crotch of his wetsuit. “Too little weight, and the current will have its way with you.”

Paul hurriedly zips up and flops off the bow, eager to join the water before our tide goes slack. With the current ebbing, he can follow the gentle flow of silt in his headlamp beam and know he’s always moving upstream and not downstream into, say, the gnarled crown of a sunken live oak. Hanging on to the anchor rope, face scrunched by his mask, Paul says, “Cheers, mate,” chomps down on his mouthpiece, then sinks from sight through a snort of brown bubbles.

Paul Burton shows off a megalodon tooth he found while scuba diving in a Lowcountry river.

Today he’s diving ancient seabed in 30.6 feet of the May River, one of the many creeks adjoining South Carolina’s Broad River network that Paul regularly hunts, preferably in winter, preferably at night when there’s less boat traffic. The Lowcountry is especially productive for “Meg” hunters like Burton. Find those areas where tides have scoured out the correct fossil strata, and you can turn the clock back 20 million years to a time when the land that is now Charleston, Beaufort, and Savannah was underwater, ruled by the largest shark that ever swam, C. megalodon. Measuring at least 50 feet and weighing more than 50 tons, this apex predator fed primarily on whales and played a major role in shaping the global marine community as we know it.

Somewhere among that biological legacy is an odd brute named Rachycentron canadum: the cobia, ling, or crab-eater. “Mr. Brown,” as Paul calls him, is the only member of its taxonomic family and somewhat prehistoric in his own right. With his fusiform body, flat head, and horizontal pectoral fins, he looks part catfish, part shark.

Each spring, Lowcountry cobia return to the tidal reaches of Port Royal Sound between Hilton Head and Beaufort, commonly known as the Broad River, the most significant cobia spawning site on the East Coast. On windless days in mid-May, they run the surface of the estuary alone or in pairs, dodging a Bubba flotilla dragging live eels below the Route 170 bridge. And if there’s one thing Paul Burton likes as much as sinking himself to the bottom of the Broad to hunt for the largest predator that ever swam, it’s cruising the surface to play cat and mouse with one of the more unusual predators that swims today. As far as he’s concerned, both are a kind of big game hunting.

“You catch a cobia on the fly, and you’ve killed a Cape buffalo,” he says in his rich South African accent.

But this is strictly an on-call fishery, requiring perfect conditions for fly rods. Conveniently for me, Paul is a partner in the real estate business at Bray’s Island Plantation, a private sporting community tucked among the live oaks and Spanish moss in the headwaters of Port Royal Sound. When conditions beckon, he can slide his boat off the plantation’s boat ramp on Haulover Creek and be in the main river hunting cobia in 20 minutes. I’d had a standing invitation from Paul since the previous December, and as May approached we’d been watching the weather, checking windfinder.com, tracking isobars, and even making the early-April dive trip for Meg teeth. Still, it would be another five weeks before my phone rang with a cobia alert:

“Steve Man, Paul. I think you better get down here. Tomorrow.”

***

ITS LATE MAY, and as we motor slowly under the abandoned train trestle downriver from Bray’s Island, Paul says, “I told myself if we see a bald eagle today, we’re going to get a fish.” Perched on the last bit of rusted metal before the bridge disintegrates into wreckage, two bald eagles nervously watch us graze the edge of their comfort zone, then take wing. From this point all the way to the ocean, we’re in cobia water.

The drill is somewhat different from a conventional flats boat. Rather than manning the bow, I stand starboard on the afterdeck, behind Burton at the helm. My cameraman, Chad McClure, grew up fishing these waters and has a keen fish eye. He gets the casting deck. In this configuration we motor toward the ocean with the throttle barely engaged, scanning for cruising ling.

A light wind is moving with the tide and ironing down the surface of Port Royal Sound, textured only by a flotsam of black needlerush, spartina grass, and shifting glare. Within 15 minutes of seeing the eagles, Paul erupts with an uncertain agitation that will intensify the more fish we see.

“Okay, right there . . . I think . . . Come on, come on . . . please, man, please . . . You see it?”

“Where?” Chad asks, both of them pointing over the tea-colored water as if their fingertips bore a third eye.

“Right there . . . twenty feet . . . I think . . . Yes! Cobia!”

This is how it works for the next two days: Chad and Paul debating with their eyesight, me trying to see what they’re pointing at, each encounter either evaporating into myth or escalating toward a cascade of shouted directions and urgent pleas for me to “Get some line out!”

When I finally sight the wake of our first cobia, it’s a 30-pounder casually finning about 20 feet off the starboard bow. From here it’s a game of trajectories as Paul bumps the throttle to flank our quarry. The trick is to place your fly ahead of the fish as the boat overtakes, and manage an arcing presentation—almost like swinging a wet fly—to trigger a follow. But the combination of moving boat, moving water, and moving fish proves demanding. As the 30-second window of opportunity slams shut, my first attempt ends in a collective groan.

Cobia often resurface after the first shot, so Paul circles back to prowl the area. In the ensuing two days we’ll spot roughly 25 cobia, get legitimate shots at 16 of them, and as far as we can tell never see the same fish twice. When it becomes apparent that this one has sounded for good, the hunt takes us downriver.

Twice more we repeat the scene, twice more ending in frustration. My casting is okay. It’s the moving pieces that throw me off, and when I do get a follow, properly managing the speed of the fly is a challenge. By 10 a.m. we’ve stalked and cast to four cobia. But I’m not playing the right mind games with the fish, and the wind is raising a slight fuzz on the surface, making them harder to spot.

At about 10:15, with sunlight igniting the tips of spartina grass in the marshes, we spot two vee-wakes heading obliquely toward the northern shoreline. Puttering alongside, I make a 15-foot starboard cast to plop the fly ahead of the fish. Before Paul’s nameless concoction of Cactus Chenille and marabou even pulses, the closest cobia turns 90 degrees and delivers an uppercut in an explosive blur of chocolate flanks and white maw. Although a small fish of 15 pounds, he bulldogs me around the gunnels twice and takes a good 10 minutes to net.

It wasn’t a classic Broad River cobia take—more a reaction than a calculated tease—but a quick release gets the skunk off, and we’re on the move again. Unfortunately, so is the wind. We motor downriver below the Route 170 bridge, hoping an outgoing tide will put us over fish following the scent of chum from local bait draggers.

We idle a grid on the southeastern side of the bridge, sector-scanning for fish slithering down a subtle wind rip. Meandering dolphins, sea turtles, baitfish, and even jelly balls all complicate the picture.

“I’m trying to pick up anything moving contrary to what my mind tells me the current is doing,” says Paul, hawkish. “The key to this game is to be ready at all times.”

Indeed, that slim vee-wake might be a glass minnow an inch under the surface, or it could be a 20-pound cobia two feet below, each a subtle disturbance in the Force, a minor ripple in the otherwise static tension that separates ocean from atmosphere. It’s not an easy game even in the best of conditions; but there’s no doubt about it: I picked the right day. The weather has played fair. Mr. Brown is in town.

VITO BERTUCCI DIED at the bottom of the Ogeechee River, trying to touch a primal and ferocious past. To handle the 10-foot tide that day, he was wearing upwards of 150 pounds of scuba gear and lead. Exactly what happened isn’t clear, but four days after Paul’s Megalodon mentor went missing, gaseous buildup returned him to the surface of Ossabaw Sound. Although “Megalodon Man,” as he was locally known, had partially cut himself out of his weight belt, the official cause of death was labeled heart attack.

After he died, Bertucci’s world-famous collection was scattered to the winds of eBay, and today, a prime tooth that once might have commanded thousands of dollars now fetches in the hundreds. But in any case, there are still few people willing to go to such extremes for either their passion or profit, and on our second day on the Broad River the sight of a diver shucking his tanks at the transom of a large center console temporarily diverts Paul’s eye from the hunt. “Gotta be—,” he mutters, following his tendency to speak in sentence fragments when excited or intrigued. “I dunno… Yeah…”

There’s no other reason to be diving there, really, but an unknown diver in such a small community of enthusiasts momentarily lures Paul off the hunt. Then, just as quickly, the spell passes. He decides to make a long run toward the bridge, where today’s fleet of leech draggers are anchored on an incoming sea, rod tips bristling, cold beer flowing in the morning sun. A light wind rustles against the tide, making it hard to tell whether to focus intently on one spot or back off, let my eyes relax, and hope to pick up some irregular part of the whole, like finding the hidden clown in a Magic Eye painting.

“If you wait for perfectly slick water, you’ll hardly ever do this,” says Paul, surveying intently from the helm. “What separates the men from the boys is being able to spot cobia in less than optimal conditions.”

Just below the bridge, a decent cobia slides past in the opposite direction, and I get off a good cast as Paul kills the throttle. Our momentum imparts a swing that excites the fish. “Strip! Strip! Strip!” Paul shouts, then “Stop! Stop! You’ve got to stop!” My stripping is one step behind his stopping, and I misjudge the speed of the boat, pulling the fly out of strike range as the fish desperately tries to close the gap. A few feet behind the transom, Mr. Brown spots the ruse and sinks from view, heading toward the bridge and its cadre of downliners hanging pogies over the guardrail. “That’s all right. He’s not gonna go home and cry himself to sleep,” Paul says, craning from port to starboard. “He’ll be looking for revenge.” A few minutes later, from atop the bridge, we hear someone’s rod snapping like a starter’s pistol.

We’ve cast to several fish, but I still haven’t put together a proper tease, moving the fly either too little or too much. Yet our prospects are improving. The tide is dead highwater slack, and suddenly, under a windless sky, we enter a 45-minute period of sun-kissed opportunity. The Teflon surface betrays any disturbance, and cruising cobia are visible in three directions.

A fly angler in a nearby skiff obliviously motors past a in steady vee wake, and quickly Paul is on the cobia’s track, closing the angle like an open-field tackler. My first cast is short, but the next one is money. When the fly starts to swing with the boat’s momentum, a full-bodied, reaching pause, strip, and reach lights up the fish. Pectoral fins erect, its confident follow becomes a close-range stalk, then a quick burst of tail and white of mouth—a strip strike, and an angry head shake.

As line peels off the reel, Paul and I are backslapping and hooting, when the line suddenly goes slack. But before we can even lick our wounds, the identical scenario unfolds again. Another fish has escaped the notice of the same skiff. We use the same approach, and it’s the same take on the same second cast. This one I stick hard. Then stick again.

Cobia usually are dogged opponents. There’s always the occasional pushover, but after about 15 minutes of trying to haul my rod tip out of the Miocene, this one has me begging for mercy.

We boat the fish, take him for the table, and soon are back on the hunt. But by then the tide has turned, and the wind shifts, raising a half-foot chop. In other words, it’s time to let the cameraman fish. With Chad in the cockpit, I point the bow upriver and nudge the throttle. Paul is sitting on the poling platform, a fly rod under one arm, poking at his cell phone.

Past the bridge, I bring the boat on plane, occasionally looking over my shoulder to see if Paul has bounced off. It probably wouldn’t matter. He once fell out of the boat in a cobia frenzy, snapped the skiff ’s sissy bar on the way overboard, crawled back in with the rod in his teeth, made a short flop cast, and hooked his fish. Cobia aren’t boat shy, and neither is Paul.

Suddenly, cruising at nearly 20 knots, an alarm sounds just above the motor shroud: “Cobia! Huge cobia! Stop the boat!” I have my doubts that anyone could spot a brown fish in brown chop at that speed, but the steel in his voice tells me otherwise. “Steve Man . . . turn around! Chad, get up there!”

Chad staggers to the bow and strips line from the 12-weight. “Jeezus that’s a big cobia,” Paul shouts, “He’s huge!”

I remain dubious, until the dark torpedo appears in a wave face at 11 o’clock, 80 feet, bearing straight toward the boat. He’s brown and broad, like the river itself. Paul is electrified, standing on the poling platform and pleading for a cast into impossible wind. But it’s too late; at 60 feet the brute slowly sinks, offering one final glimpse of his megalodonesque frame.

“Did you see him?” Paul shouts. “Every bit of seventy pounds! One of the biggest cobia I’ve ever seen.” He’s still standing on the platform as I crawl behind the helm and turn the key. “My god,” he says to no one in particular, “that was the cobia of my dreams.” ✦