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Deep Sea Chart

Type IX U-boat

shipwreck, Type IXC/40 U-boat, Kriegsmarine, Germany
1942, Germany
( 252 x 22 ft ) 1051 displacement tons, 48-56 crew
Saturday April 16, 1944
by depth charges and gunfire from destroyer escorts USS Gandy, USS Joyce and USS Peterson after torpedoing tanker Pan Pennsylvania - 44 casualties.
300 ft

U-550 emblemThe U-550 sank precisely one ship - the tanker Pan Pennsylvania - before being sunk herself. The Pan Pennsylvania was a fat prize, loaded with AvGas for Britain, with several B-25 bombers as deck cargo. But trading an oil tanker for a submarine is no way to win a war. The Pan Pennsylvania was brand new, and you can bet we launched a replacement within a week. Germany was doomed by the industrial might of the United States.

Sinking the U-550

Coast Guard-manned Destroyer Escorts USS Joyce (DE-317) & Peterson (DE-152) Sink the U-550

by Scott Price

By 1944, German submarines no longer prowled unimpeded through Allied sea lanes. The massive increase in the numbers of new merchant and escort vessels, long-range anti-submarine aircraft, and technological advances such as radar, sonar, and the evolution of anti-submarine tactics that utilized all of these new advances were factors that blunted the Nazi's U-boat offensive. A few U-boats, however, still attempted to interdict the precious convoys and Allied escort vessels, many Coast Guard-manned, remained vigilant.

On the afternoon of 15 April 1944 the 28 merchant ships of the fast-tanker convoy CU-21 departed New York harbor for Great Britain. Poor weather conditions prohibited them from forming up into their assigned positions within the convoy, which they usually did well outside of the harbor. So instead they simply formed two columns and steamed on through the night. Their escorts for the voyage, six destroyer escorts, had rendezvoused by this time and formed up around the merchantmen, much like sheepdogs guarding a flock, their sonars probing the rough water for any sign of intruders. The six escorts formed Escort Flotilla 21.5 of Escort Division 22, commanded by Coast Guard Captain William W. Kenner. His command originally consisted of six Coast Guard-manned destroyer escorts but one, the USS Leopold (DE-319) had been lost the month before south of Iceland when a U-boat torpedoed her with the loss of 171 of her crew. Another destroyer escort from the flotilla, USS Joyce (DE-317) rescued the few Leopold survivors. A Navy-manned destroyer escort, USS Gandy (DE-764), took Leopold's place within the escort flotilla.

Fortunately the weather cleared the next morning and the convoy's commodore, Captain E. H. Tillman, USN, the man in charge of all of the merchant ships in the convoy, ordered the merchant ships to take their appropriate places. Despite the care with which the escorts took in protecting their charges, an unannounced observer watched with interest as the large tankers maneuvered into their assigned convoy positions. The U-550, one of three U-boats that dared venture into the North Atlantic that spring, was on its first combat patrol. She had lain in wait outside New York harbor for just such an opportunity. Its young commanding officer, Kapitanleutnant Klaus Hanert, saw what every U-boat commander looked for: a straggler. This merchant ship, a tanker with a full cargo of aviation fuel, was well behind the forming convoy. What luck! Not only was she a straggler, but she was also one of the most valuable targets any U-boat could hope to attack.

As the tanker sailed ever closer to the submerged U-boat, Hanert's crew prepared their attack. He checked the range and bearing to the target and this data was fed into the torpedo aiming computer which then prepared the torpedo for its run. Once ready, Hanert gave the order to fire. A little after 0800 the single torpedo hit the port side of the SS Pan Pennsylvania, the largest tanker in the world at that time. It carried a highly combustible cargo of 140,000 barrels of 80-octane aviation fuel, a fact not lost on its 50-man crew or the 31 members of her Naval Armed Guard.

Many men panicked and leapt into the water while others attempted to launch a lifeboat without waiting for the order to abandon ship or for the Pan Pennsylvania to come to a complete stop. The lifeboat capsized and spilled the men into the frigid water. Luckily the cargo did not explode but only began to catch fire. But the explosion did cut communications between the bridge and the engine room. The tanker's master sent the chief engineer to check on the conditions in the engine room while he informed the convoy commander of his predicament. He then searched the ship to make sure that no remaining crewmen were trapped as the huge tanker began to settle by the stern.

Pan Pennsylvania burns in the background as the stricken U-550 surfaces

In an effort to evade an inevitable counterattack by the escorts, Hanert attempted to place his submerged U-boat near the sinking tanker, hoping it would mask his presence. Unbeknownst to him, however, the escorts were also heading in that direction, as Kenner immediately ordered the Joyce to retrieve the survivors. He then ordered USS Peterson and the Gandy to screen the rescue effort, and the three destroyer escorts broke formation and sailed toward the stricken tanker, all with their sonar equipment actively pinging the area. The situation on board the Pan Pennsylvania worsened. The chief engineer inspected the engine room and saw what the men feared most. A fire had broken out and was spreading. The engineer reported back to the tanker's master who then gave the order to abandon ship. The tanker continued to settle by the stern and developed a list to port but the crew managed to launch two lifeboats and three life rafts before the ocean's surface began to wash over the tanker's large deck.

Joyce hove to, near the doomed ship, and its crew quickly went to work retrieving the survivors. There were so many, in fact, that Peterson had to lend a hand. Joyce's crew pulled 31 men from the lifeboats and rafts and Peterson's crew saved 25, but 25 others remained unaccounted for. The tanker continued to settle and then slowly capsized. As Joyce prepared to get underway, her sonar operator obtained a contact at 1,800 yards. Hanert, growing uneasy so near a sinking ship, had attempted to slowly and quietly move away from the drowning behemoth. U-550's engineer later told interrogators, "We waited for your ship to leave; soon we could hear nothing so we thought the escort vessels had gone; but as soon as we started to move -- bang!"

U-550 surfaces

Joyce's commanding officer, Lieutenant Commander Robert Wilcox, USCG, gave orders to prepare to attack and brought the warship to flank speed. Joyce radioed the other two destroyer escorts about the contact as her crew prepared to drop depth charges. Gandy formed up behind Joyce to carry out a synchronized attack. Peterson sailed close behind her sisters. As Joyce passed over the sound contact, her crew dropped 13 depth charges, all set to a shallow setting. In a perfectly timed and executed attack the depth charges bracketed the submerged submarine and exploded, literally blowing the U-550 out of the water. The depth charges were so well placed, reported another German survivor, that one depth charge actually bounced off the submerged U-boat's deck plating before it exploded.

The sailors saw the U-boat's bow break the surface and both Gandy's and Peterson's commanding officers gave the order to ram. At the same time, the three destroyer escorts opened fire on the hapless Germans but the two Coast Guard-manned warships ceased firing as the Gandy (USN) unadvisedly sailed between them and the submarine. Peterson veered off as Gandy closed with the German submarine.

U-550 surfaces

Gandy slammed in to the U-550 abaft the conning tower, damaging the U-boat further and Peterson fired two depth charges from her "K" guns, which exploded along the side of the German submarine. Once Gandy was clear, all three destroyer escorts again opened fire, preventing the German crew from attempting to man their deck guns. Nevertheless a number of U-boatmen attempted just that and were cut down as they exited their hatches. When Gandy ceased firing, more Germans attempted to man the after machine gun and actually managed to open fire briefly before the concentrated fire from all three destroyer escorts mowed each one down and laid waste to the conning tower.

U-550 continued taking on water and dipped lower within the sea. The surviving U-boatmen, realizing their submarine was doomed, first set their scuttling charges and attempted to abandon ship. The charges exploded quickly, and the U-boat quickly settled by the stern and then sank beneath the waves, trapping most of the crew within its hull. The destroyer escorts ceased firing and sailed in close to rescue the few survivors, men who they were attempting to kill only a few moments before. Joyce managed to pull thirteen German sailors from the water, including U-550's commander, but the rest of the U-boat's crew went to the bottom with their submarine. As the three destroyer escorts sailed back to the convoy, the Gandy's crew patched the damage they received when they rammed U-550. The now-capsized Pan Pennsylvania lay against the horizon, a solemn reminder of just how deadly the Battle of the Atlantic still was. The smoking hulk was sunk by gunfire two days later.

U-550 funeralOne of the rescued U-boatmen, Heinrich Wenz, later died from his wounds. LCDR Wilcox conducted a funeral service and then committed Wenz's body to the sea. The convoy continued on to Britain, despite the loss of the Pan Pennsylvania, and arrived there unscathed. In a gruesome side script to the story, apparently some of the German crewmen survived the sinking of their U-boat in their forward watertight compartments. Over the next few hours or days they attempted to eject from their sunken submarine to reach the surface with their escape equipment, but unfortunately perished in the attempt. A few of their bodies were recovered floating off the coast a few days later, fueling speculation that some Germans actually made it to shore along the U.S. coast.

As for the attack, a mere thirteen minutes passed from the moment Joyce detected U-550 to the time the U-boatmen abandoned ship, an indication of the effectiveness of Allied anti-submarine capabilities and the teamwork demonstrated between the escorts.

The Navy ended up crediting all three destroyer escorts with the kill, but noted, "the [depth charge] pattern dropped by the Joyce was accurate. There is no doubt that it threw the sub out of control and caused it to surface, if not causing greater damage."

U-550 survivorsRight: U-550 survivors aboard Joyce

Both Hanert and Wilcox survived the war. One of the surviving junior officers of the U-550, Hugo Renzmann, met with Wilcox in 1960 in New York City to discuss the battle. As a Coast Guard press release noted, "they shook hands and immediately began relating events which led up to their first meeting. It was like two avid sport enthusiasts telling each other how they won or lost the previously played game."

from Coast Guard records

USS Joyce
USS Joyce

USS Peterson
USS Peterson

USS Gandy
USS Gandy ( after the war, in Italian service )

German sailors abandon ship
German sailors abandon ship
German sailors abandon ship
German sailors continuing the fight from their sinking sub with the deck guns. ( Various views of the same photo )

If this doesn't make sense, it is because it is not true - the Germans never fired on the DEs. Look at the picture - no one is manning a gun, the guns are all pointing at the sky. The three DE's, however, surrounded the sinking sub in a crossfire, attacking fiercely and probably taking hits from each-other in the process. A stray shot from the Gandy even set the Pan Pennsylvania on fire.

The U-550 sinks
The U-550 sinks
The U-550 sinks ( ironically, a day before her victim ) Photographed from USS Joyce DE-317

Divers Find Sunken German U-boat Off Massachusetts Coast

Friday Jul 27, 2012 5:53 PM

Researchers have discovered a World War II-era German submarine nearly 70 years after it sank under a withering U.S. attack in waters off Nantucket.


BOSTON -- Divers have discovered a World War II-era German submarine nearly 70 years after it sank under withering U.S. attack in waters off Nantucket.

The U-550 was found Monday by a privately-funded group organized by New Jersey lawyer Joe Mazraani.

"They've looked for it for over 20 years," Mazraani, a shipwreck diver, told The Boston Globe. "It's another World War II mystery solved."

In the second trip in two years to the site by the team, the seven-man crew using side-scan sonar located the wreck listing to its side in deep water about 70 miles south of Nantucket.

Sonar operator Garry Kozak said he spotted the 252-foot submarine during the second of an exhausting two days of searching. Kozak said the team asked him if they'd found it, then erupted in joy without a word from him.

"They could see it with the grin ( on my face ) and the look in my eyes," Kozak said.

The crew had searched 100 square miles of ocean, the Globe reported. Traveling at five knots, the ship scanned the vast expanse for signs of the sunken vessel, a tedious process crew members likened to "mowing the lawn."

Mazraani dove down to confirm the discovery with pictures, the Globe said.

On April 16, 1944, the U-550 torpedoed the gasoline tanker SS Pan Pennsylvania, which had lagged behind its protective convoy as it set out with 140,000 barrels of gasoline for Great Britain, according to the U.S. Coast Guard website and research by Mazraani.

U-550 sidescan
This sonar image provided by GK Consulting & AWS Expeditions / Joe Mazraani, shows a World War II-era German submarine, U-550, found by a team of explorers Monday on the floor of the Atlantic Ocean 70 miles south of Nantucket Island, Mass.

The U-boat slipped under the doomed tanker to hide. But one of the tanker's three escorts, the USS Joyce, saw it on sonar and severely damaged it by dropping depth charges.

The Germans, forced to surface, manned their deck guns while another escort vessel, the USS Gandy, returned fire and rammed the U-boat. The third escort, the USS Peterson, then hit the U-boat with two more depth charges. The crew abandoned the submarine, but not before setting off explosions to scuttle it. The submarine hadn't been seen again until Monday.

The U-550 is one of several World War II-era German U-boats that have been discovered off the U.S. coast, but it's the only one that sank in that area, Mazraani said. He said it's been tough to find largely because military positioning of the battle was imprecise, and searchers had only a general idea where the submarine was when it sank. Kozak noted that the site is far offshore and has only limited windows of good weather.

The other team members were Steve Gatto, Tom Packer, Brad Sheard, Eric Takakjian and Anthony Tedeschi

Mazraani is cagey about the vessel's precise location, saying only that it's in deep water. Mazraani's said his best estimate was that the team spent thousands of dollars of its own money on the expedition. He joked that no one on the team, whose members range in age from the mid-20s to mid-50s, stands to make money from the find unless someone writes a book.

Mazraani said the next step is to contact any sailors or their families from the escort vessels, the tanker and the German U-boat to share the news and show the pictures. Another trip to the site is coming, he said, adding the investigation has just started.

"The history behind it all is really what drives us," Mazraani said.

This article includes reporting by The Associated Press.

Where Divers Dare
Part of the Pan Pensylvania was found upsidedown in 240' of water in 1995. The stern broke off and was found 20 miles away. The U-550 was found in 2012 at about 300', close to the edge of the continental shelf.

Where Divers Darereprinted from
Where Divers Dare
by Randal Peffer


July 22, 2012

A black night on the North Atlantic. Joe Mazraani's eyes feel like they're popping out of his skull as he sits in the steering seat on the dive boat Tenacious. The vessel is lumbering westward at 10 knots, giving off the sour scent of diesel exhaust. It's only about 2240 hours, at night, but it feels like long past midnight. Mazraani squints to see beyond the glow of the chart plotter, the depth sounder screen, the radar, and the compass. More than a few people have noted that when he's at the helm of his dive boat, he puts them in mind of George Clooney in The Perfect Storm.

He has been peering into the gloom for hours, days. Years, if he has to admit the truth about the depth of his obsession for this hunt. He knows that it's not rational, but at some point tonight he has started to imagine flailing, beckoning arms, the flashes of white life vests among the dark waves. Then German cries of "Helfen sie mir." Help me.

He wonders if he's alone with these ghosts. Or are the other men on Tenacious haunted, too? But, of course, they are. Why would they be out here on such a night so far from land if they were not spellbound, caught in the thrall of the dead, the dying, and the mysteries that surround them? Possibly divers Brad Sheard, Eric Takakjian, and Anthony Tedeschi, sleeping in their forecastle berths, are dreaming of the naval battle that took place here, near the edge of the continental shelf, 70 miles south of Nantucket Island on April 16, 1944. It was a day when the Battle of the Atlantic exploded in chaos on America's doorstep.

Maybe sonar operator Garry Kozak, curled on the berth behind the steering station on a short break, is picturing the morning when a torpedo from U-550 split open the side of the tanker SS Pan Pennsylvania on this patch of ocean. Maybe as he snores softly, Kozak's seeing the Pan Penn list suddenly 30 degrees to port. Or perhaps he's seeing twenty-five American men from the tanker scrambling into a lifeboat, then seeing the ship capsize.

Maybe divers Steve Gatto and Tom Packer are sharing the same nightmare as they sit side by side on a bench seat, snacking on peanuts and gazing into the sonar monitor on the galley table in front of them. Gatto and Packer have been deep wreck diving buddies for so long, they sometimes feel uncertain where one man's mind leaves off and the other's picks up.

Maybe together they are lost in the moments when depth charges from the destroyer escort USS Joyce drive the German sea wolf to the surface. Perhaps they are witnessing the withering attack from three destroyer escorts, hearing the pock-pock-pock of 20mm cannons firing as the Americans' shells turn U-550's conning tower into Swiss cheese. Or possibly they are wondering what it must have been like to be one of those German boys who abandoned his sub for the water as the U-boat was sinking. The Americans rescued only thirteen men. That water's so cold. Nobody knows better than divers such as Gatto and Packer how frigid and unforgiving the North Atlantic can be. They've witnessed too many men die in these waters for real, not just in a nightmare hijacked from 1944.

Joe Mazraani hears a groan. It's Pirate, his Portuguese water dog sleeping at his feet. Mazraani shivers a little. But it's not Pirate's groan or the chill of the night air that rattles him. It's this place and its phantoms. If you ask him, he'd tell you that you don't want to ever come to a watery graveyard like this without a serious band of brothers. You don't want to be hunting for a lost U-boat far at sea with bad weather coming without the best of shipmates. You sure as hell don't want to be thinking of diving 300 feet down in black waters unless you have someone you really trust to watch your back.

Ashore he works as a criminal defense attorney in New Jersey, but out here he's the captain of Tenacious. Like all of his shipmates tonight, he's not just a man starting to face off with ghosts. He's a man on a mission. They all are.

This trip marks their second summer of active searching, and the pressure's building. While Mazraani's team has been hunting for U-550 in absolute secrecy, another team, led by a respected New England wreck diver, has been publicizing its own search for the 550 with YouTube videos. A recent one shows the New England team laying a wreath on the water over the wreck of the tanker blown apart by the U-boat. And rumor has it that yet another team is also trying to mount a search for U-550. Bottom line: if the Tenacious divers don't find the 550 on this trip, someone else will probably beat them to the long-lost submarine.

Not even treasure is more compelling to these divers than being the first humans on a wreck. And treasure, of a sort, is definitely important to wreck divers. They bring back artifacts all the time, spend tens of thousands of dollars to restore them and display them at their homes and at museums and dive shows. If this wreck were a commercial ship like the liner Andrea Doria, salvaging artifacts from the wreck would be fair game. The U-550 discovery divers have plates, glasses, silverware, and bronze nautical hardware from dives on the Doria. Wreck divers see their artifact collections as preserving history, and at times they share their collections with museums. Tom Packer was one of the divers who helped to salvage a bell off the Doria back in 1985. Gatto has a helm, a steering wheel, from the liner. He, Packer, and diver John Moyer have filed legal papers in court, which makes them Salvors in Possession of the wreck.

But divers cannot own a warship such as U-550. Maritime law unequivocally states that the wreck of a warship forever belongs to the country it served. It's a way of honoring and preserving war graves. The divers aboard Tenacious respect that. Instead of harvesting artifacts from the sub, they want to find 550 to get as close as they can to a moment when the Battle of the Atlantic flared right off US shores.

U-550 is the last unfound German U-boat known to have sunk in diveable waters off America's East Coast. For divers Eric Takakjian and Brad Sheard, the hunt to unravel the mysteries of this submarine goes back twenty years. For others, such as Gatto and Packer, men in their fifties, this dive expedition is another chance to bond with some of the few men who really understand them. They are divers whose names rise from the pages of Shadow Divers as some of the most seasoned deep wreck divers in the Northeast.

All of these guys feel the lure of unearthing history. They crave the opportunity to bear witness to the buried time capsule that is a previously undiscovered wreck. They seek the challenge of the search above and below the water, the planning for both the hunt and the deep, dangerous dive. They love the anticipation of a long and sometimes rough boat ride, crossing the water to the middle of nowhere. They thrill to the interface with sea creatures such as lobsters, immense codfish, sea turtles, rays, dolphins, whales, and white sharks. They relish plunging to places few humans see and fewer return from. Finally, they cherish the chance to resurface in the world of the living again with an artifact such as a bell or a porthole that says, "I have been to the underworld, the land of the dead. I have come back to tell you all." Strong drugs.

And, while Packer rarely puts his motives into words, he's here to watch out for his dive buddies, especially the totally pumped younger men whose enthusiasm for their sport can drive them to take terrible risks. Packer knows how easy it is to get lost inside a wreck or trapped by debris. Diving gear has gotten so much better since he, Gatto, Sheard, and Takakjian started diving more than three decades ago, but equipment is never fail-safe. And when you are going as deep as 300 feet, you probably can't make it to the surface and live if you run short of air down there. Every man on Tenacious has his own personal collection of almost-died stories. All of them have known men who have died diving wrecks. Several of them have led the way to recover dead divers from the dark corridors of a shadowy ghost ship.

But for thirty-four-year-old Mazraani, and the even younger Tedeschi, danger beckons. Finding and diving the U-550 is the ultimate adventure, one seductive enough to prompt Mazraani to buy his own dive boat to chase the dream. It's a fantasy so alluring that the young attorney has hired Kozak to use his high-tech sonar "fish" to scan the inky water for a lost phantom.

And right now it looks like Kozak's fish has a problem.

"What the hell?" Packer's voice brings Mazraani back to the present.


"The monitor just freaking froze," says Gatto.

Somebody wakes Kozak.

"Hold your course," he says groggily, "until I can fix this thing."

For the past fifteen hours the expedition team aboard Tenacious has been towing their sonar fish, a 6-foot-long, torpedo-shaped echo sounder on a wire, 440 yards behind the boat, 250 feet below the surface of the Atlantic. The dive boat has been steaming back and forth across an 84-square-mile grid where the divers think U-550 lies.

This kind of searching is what deep-sea hunters call "mowing the lawn." It's mind-numbingly boring, and yet it demands total attention to every little detail observed by the sonar fish if you want any hope of finding your needle in the haystack. In this case the needle is the wreck of a U-boat sent by Hitler to prey on American merchant shipping sixty-eight years ago. A predator sunk by Coast Guard and Navy sailors. The alleged grave of more than forty men.

"You want me to turn around for the next pass to the east?" asks Mazraani.

"No. Just keep going," says Kozak. Tenacious moves beyond the perimeter of the search grid.

Mazraani nods, reminds himself to focus, stick with the program.

It's only a minute or so before the sonar monitor's online again. Mazraani's thinking about turning his boat back to the search grid when one of the guys at the monitor says, "Holy shit. We're going over something."

Instinctively, Mazraani hits the key on the laptop that is his GPS chart plotter to mark the position.

Gatto, Packer, and Kozak are watching a strange bottom anomaly coming into view on the side scan, a mysterious blip. It looks too large to be a submarine, but who knows?

"This could be big," someone's voice cracks. "Wake the others."

It's 2245 hours, July 22, 2012, and maybe these deep wreck hunters have just found their holy grail. But nobody's going down there to see. Not now. Even on the sonar monitor the ocean looks dark as all hell.

The entire story, from the sinking of the Pan Pennsylvania to the discovery of the U-550, and the true final moments of the sub, is covered in this excellent book.

Pan Pennsylvania

Deep Sea Chart

Shipwreck Pan Pennsylvania

shipwreck, tanker, USA
1943, Norfolk VA, USA
( 516 x 70 ft ) 11017 gross tons
Sunday April 16, 1944
torpedoed by U-550, then shelled and sunk by USS Sagamore - 60 survivors
240 ft ?

Pan Pennsylvania burns in the background as the stricken U-550 surfaces
Pan Pennsylvania burns in the background as the stricken U-550 surfaces

USS Sagamore
USS Sagamore



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