It was no surprise the dramatic Coast Guard video quickly went viral.

Shot on a coast guardsman's helmet camera, the one-minute clip posted to the Department of Defense's imagery website captured the remarkable end of a June 18 high seas pursuit that ended with one team member leaping aboard a moving submersible and pounding on the hatch until suspected drug runners opened up.

But the story of how Coasties took down the so-called “narco sub” began about 12 hours before the video took place, according to Capt. James Estramonte, the commanding officer of U.S. Coast Guard Cutter Munro, the high endurance vessel credited with its seizure.

(U.S. Coast Guard Pacific Area)

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Early that June morning, Estramonte received intelligence on the narco sub from a Navy P-3 surveillance aircraft, acting as an airborne early warning system for the cutter, which was then patrolling in the Pacific Ocean roughly 200 miles west of the Colombia-Ecuador border.

Estramonte knew he had to hit the gas to catch the suspected smugglers, which were about 250 miles away and moving north. It was yet another lead coming into the Alameda, California-based cutter, which was keeping busy on its first counter-drug patrol of its second deployment, after commissioning in 2017.

Despite its fairly recent introduction to the fleet, the Munro's historic lineage from World War II gives its crew plenty of inspiration for bravery. In Sep. 1942, Signalman 1st Class Douglas Munro led five small boats to the shores of Guadalcanal in the Solomon Islands to rescue a battalion of beleaguered Marines, and at one point, positioned his craft between Japanese machine guns and Marines to shield them from fire. With his dying breath, Munro's final thought was to ask whether the Marines were safe: “Did they get off?”

Although Munro was mortally wounded in the rescue, his actions earned him the Medal of Honor for saving the lives of 500 Marines. The Munro is the second cutter named in his honor, and Estramonte told Task & Purpose the vessel's history has created a close bond between his Coasties and the Marines.

Capt. James Estramonte, commanding officer of the Coast Guard Cutter Munro (WMSL 755), and Senior Chief Petty Officer Leslie Hearn, the Munro's command senior chief, attend a rededication ceremony for Douglas Munro's memorial in Honiara on Guadalcanal, Solomon Islands, Nov. 27, 2018.
(U.S. Coast Guard/Petty Officer 3rd Class Matthew West)

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After assessing the intelligence, Estramonte ordered the cutter to 25 knots (about 28 mph) to catch the sub, which he estimated had about 1,000 miles left to reach the United States. Despite the slow speed of the sub, it would still take about 10 hours for Munro to get close enough to launch its boats and a helicopter.

Meanwhile, inside the custom-built sub were five men, eating store-bought snacks and drinking bottles of water and soda alongside 17,000 pounds of cocaine.

“These vessels are custom built for one purpose – to transport as much drugs as possible,” said Lt. Cmdr. Stephen Brickey, a Coast Guard spokesman.

Inside the narco sub(U.S. Coast Guard photo)

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With just a few small forward-facing windows giving the sub driver a view not much more than a few hundred yards ahead, the voyage was perilous — even without a potential Coast Guard presence.

“Their visibility is pretty limited. It's pretty tough conditions for these five guys,” Estramonte said. “There's a chance they didn't even know we were there until we started banging on the hatch.”

With its low-profile and proximity to the waves, SPSS vessels are incredibly difficult to spot, and even more difficult to seize — Brickey likened it to the “White Whale” in one interview — since drug smugglers typically scuttle the vessel if they find out they're being tracked.

Their reasons are simple: It's a lot harder to convict someone of smuggling drugs if the drugs are gone.

At 20 miles out from the sub, members of the boarding team launched in two small boats, a 26 foot boat called a Mark 4, and a 35-foot long range interceptor. On board were 13 coast guardsmen specially-trained in boarding vessels, including members of its elite Tactical Law Enforcement Team, which often accompany Navy ships on counter-drug missions, although Estamonte jokingly admitted that jumping onto a sub in choppy waters may not be in the training manual.

“I don't know if there's any specific training” that helps you jump onto a narco sub, Estamonte said, but “these guys specialize in doing this.”

In addition to the small boats, the Munro also launched its helicopter to provide sniper overwatch with a .50 caliber rifle while sending updates to the captain throughout the operation.

The two boats approached from different sides of the sub's stern. As one inched closer, a coast guardsman shouted in Spanish, “stop your boat!” but it continued, likely oblivious to the shouting. Then one boarding team member had a different idea in mind: Jump on top of the thing and start banging on the hatch.

“It's gonna be hard to get on!” he said, before he and two others jumped on the back, water splashing over their boots. Back at the Munro, the captain could only get the play-by-play from the helicopter, like a football coach who can't see the field. First man on, then second man, Estramonte would hear, and then: the boarding team has positive control of the vessel.

Fortunately, the men on board the sub opened the hatch and were quickly hauled out without a fight, though the boarding team was armed with pistols and ready for the worst.

U.S. Coast Guard Cutter Munro crew interdicts suspected drug smuggling vessel
(U.S. Coast Guard Pacific Area)

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Though the video ended once the chase was over, guardsmen had to spend the next 12 hours unloading the huge haul of coke, worth an estimated $232 million. And then finally, after many photos were taken and the sub was given a final sweep for evidence, it was intentionally scuttled.

“It doesn't go down as easy you might think,” Estramonte said.

All told, the Munro nabbed roughly 31,000 pounds of narcotics from eight suspected drug smuggling vessels during its deployment, to include the “narco sub.” That earned them a welcome home speech by Vice President Mike Pence, the satisfaction of a job well done, and widespread praise from civilians and veterans alike.

“It takes every single member of a coast guard crew, and every single ounce of effort that they put into their work — whether they operate, navigate, repair, clean, mend, feed, support, mentor, or lead — in order to safely and successfully execute these dangerous missions,” said Brickey, the Coast Guard spokesman.

“While this case is a great example of operations that occur multiple times a day, every day, in the U.S. Coast Guard, it more importantly demonstrates the courage and commitment that our members regularly put forth in service to our nation.”