A deep dive with Kostas Thoctarides

What does it take to locate a submarine lost for more than eight decades? Through meticulous research and a passion for history Kostas Thoctarides recently announced his eighth sub wreck discovery, HMS Trooper, as reported on Divernet. He shares some of his experiences in underwater exploration in conversation with ROSS J ROBERTSON, with additional research by Dr KONSTANTINOS GIANNAKOS

Every corner of each room was filled with towering, disorderly stacks of books, and shelves groaned under the sheer weight of accumulated knowledge. Nautical artwork adorned the walls, punctuated by the occasional brass diving helmet or compass – silent relics of the deep.

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Stepping into this suburban Athens apartment felt like crossing into another world, a sacred space where history, exploration and the sea coalesced. The air seemed to whisper with the mysteries of the ocean. 

My host welcomed me with a gracious nod, gesturing toward a long table that had clearly served as a hub for countless meetings and profound discussions. His warm, easy demeanour put me instantly at ease, and soon our conversation began to flow. 

As he deftly retrieved books from the shelves or produced well-worn folders to underscore a point, it became clear: I was in the presence of someone whose vast knowledge was rivalled only by his boundless passion for all things maritime.

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It shouldn’t have come as a surprise. After all, I was speaking to Kostas Thoctarides – a legend in the international diving community, whose name resonates like the depths he has explored.

Dive logbook

Kostas’s personal dive logbook deserves to be enshrined as a national treasure. Since his first scuba dive in 1986, he has explored countless shipwrecks, including an impressive number of submarines. Notably, in 1997 he discovered HMS Perseus, which had been struck by an Italian mine in December 1941 and now lies at 52m between the Greek islands of Zakynthos and Kefalonia. 

Through pure research, he was also the first to identify U-133, struck by a Greek mine on 14 March, 1942, shortly after leaving the German U-boat base at Salamis, near Athens. It now rests 72m deep off the island of Aegina in the Saronic Gulf.

Kostas’ journey into the deep began after completing specialised training in mixed-gas deep diving in 1987, when he was propelled into the demanding world of professional diving. Trained by prestigious state schools in the UK (HSE) and France (INPP & COMEX), he rapidly advanced to the highest levels.

Embracing cutting-edge technologies, he achieved certification from the renowned French company COMEX as a pilot of the submersible Thetis for the National Centre for Marine Research, and as chief ROV pilot. 

His expertise has led him to explore and document hundreds of 20th-century shipwrecks, including historic vessels such as the Hellenic destroyers Vasilissa Olga and Hydra, the submarine Katsonis, and the ex-ocean liner HMHS Britannic, sister-ship to the Titanic.

He has also explored the wreck of the Hellenic Navy fast-attack torpedo boat P-25 Kostakos, which sank in November 1996 during naval exercises following a collision with the passenger ferry Samaina off the island of Samos, with the loss of four crew-members.

“One of the most challenging mixed-gas dives of my career took place in 1996, during the height of the Greek-Turkish crisis at the Imia islets,” Kostas recalled. “Amid heightened tensions, a Greek Navy AB 212 helicopter tragically crashed north of the islets, with its three-man crew lost at sea. 

“As part of the recovery operation, I dived to a depth of 96m, navigating politically tense and physically turbulent waters to locate and recover the sunken PN21 helicopter,” he said, underscoring the extent of his experience in high-stakes underwater operations.

Accolades

Kostas has been honoured many times for his services to Greece. Former Minister of National Defence Gerasimos Arsenis personally commended him for his contributions, as did Lt-General Kapravelos, Chief of the Hellenic Army General Staff, for the recovery of two missing soldiers from Lake Vouliagmeni in 1993. 

In 1996 he was again recognised by the Hellenic Navy General Staff and Chief Vice-Admiral Paliogiorgos for his critical role in recovering the PN21 helicopter. That same year, he was honoured once more by Vice-Admiral Paliogiorgos for leading the search and recovery of P-25 Kostakos’s missing crew.

His expertise has also earned him accolades beyond the military. In 2003, the Hellenic Ministry of Transport & Communications, along with the Air Accident Investigation and Aviation Safety Board, awarded him an honorary distinction for his contributions to recovering downed aircraft in Greek waters. 

In 1997 the International Academy of Letters & Arts presented him with the gold medal and the prestigious Prize of Virtue and Courage. Additionally, in 2000 the British Submarine Old Comrades Association honoured him for discovering Perseus.

Relentless Pursuit

Kostas is an accomplished author and a producer of films and TV documentaries, specialising in the exploration of 20th-century historical shipwrecks.

In recent years he has continued to embrace technology for pushing the boundaries of deeper wreck discoveries, using ROVs that can withstand extreme pressures and conditions far better than human divers.

“Remotely piloting an ROV is far from easy, as my daughter Agapi can tell you,” he chuckled. “She’s the first certified female ROV operator in Greece. It takes not only a specialised skill-set but also a ‘sixth sense’ to do it well,” he added proudly. 

That said, his scanning equipment largely consists of a modified, off-the-shelf fish-finder sonar rather than specialised gear, underlining that skill and experience outweigh the need for expensive gadgets.

What sets Kostas apart is a relentless passion that drives him to conduct multi-layered research, meticulously piecing together historical records and eyewitness accounts. With every wreck he uncovers, Kostas says he experiences an exhilarating rush – the thrill of revealing stories that only the physical evidence can fully provide.

“In November 2021, I discovered the WW2 Italian submarine Jantina, torpedoed by the British submarine HMS Torbay on 5 July, 1941. It was lying at a depth of 103m south of Mykonos, but there was a twist – the entire bow section was missing. It wasn’t anywhere to be found, and that really bothered me. It took me three more years to locate it.”

“You searched for three years?”

“Whenever I could, yes. It turned out that the bow had sunk immediately, but the rest of the vessel continued to power ahead before finally going down.

“Finding the bow was crucial – not only did it confirm the wreck’s identity, as it had a unique net-cutting mechanism, but it also revealed that the torpedo-hatches were closed. That meant that the crew had been taken completely by surprise by HMS Torbay.”

“Persistence has to be the key to your success,” I remarked.

“Absolutely,” he replied enthusiastically. “It took me only 25 years to find the submarine HMS Triumph in 2023!”

I knew the story well – Kostas had eventually found spent torpedoes on the seafloor, which helped him to discover the historically important wreck. 

Following the German invasion of Greece in April 1941 and the subsequent evacuation of British and Commonwealth forces, there had been a scramble to evacuate stranded soldiers while simultaneously establishing a covert network of local spies and informants to sabotage the Axis occupation. 

The loss of Triumph in early 1942 during a top-secret MI9/SOE mission known as Operation Isinglass dealt a severe blow to British intelligence operations in the region, not least because of the political infighting it caused.

Searching online

I wondered if the Internet had proved helpful in Kostas’s researches. “Only in a limited way, as most primary source materials are still archived only on paper,” he said. 

“Let me give you an example: On 22 October, 1943, during operations near the island of Kalymnos, the Greek destroyer RHN Adrias struck a mine that tore off its entire bow, but it didn’t sink.

“The destroyer sent in for rescue, HMS Hurworth, hit the same minefield and sank, leaving the badly damaged Adrias to rescue its survivors as well as its own crew. 

“Against all odds, Adrias famously managed to limp back to Alexandria, Egypt, all the while avoiding Luftwaffe attacks, eventually arriving on 6 December to a hero’s welcome – understandably.”

Kostas reached for a large file, pulling out an old chart that he carefully unfolded on the table before me. It showed a series of meticulously plotted parallel lines, each connected by a 180° turn.

“After the war, the captain of the Adrias, Ioannis Toumbas, was tasked with clearing the very same minefield that had crippled his ship,” he went on. “This is the chart from that mine-sweeping operation, and it eventually helped me locate the missing bow of the Adrias.” From his tone, the discovery had been not just a historical triumph but a deeply personal one.

“Such charts are not on the Internet – even knowledge of them isn’t online – so a real researcher still has to get his or her hands dirty, so to speak,” he concluded with a smile.

The 8th Submarine: HMS Trooper

“And your latest discovery? Can you tell me a little more about HMS Trooper?” I asked. 

“Well, after 81 years it has been found – although it was no small feat and took many attempts and countless hours of meticulous research.” 

The submarine lies at a depth of 253m between the islands of Ikaria and Donousa. “It’s broken into three distinct sections: the bow, midsection and stern. The condition of the wreck indicates a violent sinking due to a mine detonation.”

“Mines seem to have been the bane of submarines,” I commented. 

“Yes, indeed. They were almost impossible to detect, especially from a submarine. You wouldn’t know they were there unless you snagged a cable or it struck the hull – by then, it was already too late. They claimed the lives of so many. 

“All 64 crew-members aboard the Trooper lost their lives, and a crucial part of discovery is ensuring that their resting place remains undisturbed. Finding Trooper not only resolved an eight-decade-old mystery, but also serves as a solemn reminder of the sacrifices made by those brave men.”

Ripples of reflection

For Kostas, his discoveries are not just about solving mysteries – they’re about preserving stories that might otherwise be lost to time. His work serves as a bridge between history and the present, reminding us of the profound connections we share with those who came before, and of the importance of honouring their legacies through exploration and knowledge. 

Scuba and remote diving allow us to explore these underwater realms, enabling us to recover and safeguard a rich history that would otherwise remain hidden from us forever.

Kostas Thoctarides runs the companies ROV Services and the Planet Blue dive-centre at Lavrio near Athens.

Also on Divernet: Misheard voice threw HMS Trooper sub wreck-hunters for 25 years, Greek sub-hunter finds missing bow, Unyielding pursuit: The finding of WW2 sub HMS Triumph, Sub-hunter tracks down HMS Triumph off Greece, Tragic WW2 wreck located at 153m off Hydra, Mystery wreck found off Greek island, Greek wreck-hunter solves 1959 mystery