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

My host welcomed me with a gracious nod, gesturing toward a long table that 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 unmistakably clear: I was in the presence of someone whose vast knowledge was only rivalled by his boundless passion for all things maritime. It shouldn’t have been a surprise, after all, I was speaking to Kostas Thoctarides – a true legend in the international diving community, a man whose name resonates like the depths he has explored.

Ir Thetis Remora. Photo: Supplied

Enviable accomplishments

Kosta’s personal dive logbook deserves to be enshrined as a national treasure. Since his very first scuba dive in 1986, he has explored countless wrecks across the ocean floor, including an impressive number of submarines. Notably, in 1997, he discovered the legendary submarine HMS PERSEUS which was struck by an Italian mine in December 1941 and now lies at 52 m (171 ft) between the Greek islands of Zakynthos and Kefalonia. Through pure research, he was also the first to identify U-133, which was struck by a Greek mine on 14 March 1942, shortly after departing from the German U-boat base at Salamis, near Athens. It now rests at a depth of 72 m (236 ft) off the island of Aegina in the Saronic Gulf.

Torpedo tube 7 on the upper starboard bow with the cap open without torpedo.

His journey into the deep began after completing specialised training in mixed gas deep diving in 1987, a skill that propelled him 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 professional levels.

Embracing cutting-edge technologies, Thoctarides 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 pilot of Remote Operated Vehicles (ROVs). 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 legendary ocean liner HMHS BRITANNIC, sister ship to the TITANIC.

Kostas Thoktarides. Photo: Supplied

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. Four crew members were tragically lost.

“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,” Kosta recounts. “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 96 metres (315 ft), navigating politically tense and physically turbulent waters to locate and recover the sunken PN 21 helicopter,” he adds, further underscoring his extensive experience in high-stakes underwater operations.

Underwater photographs of the Trooper wreck compared with the recognition and identification points.

Accolades galore

Kosta has been honoured numerous times for his exceptional service to Greece, earning recognition from the highest ranks of military and government authorities. Former Greek Minister of National Defence, Gerasimos Arsenis, personally commended him for his contributions, as did Lieutenant General Kapravelos, Chief of the Hellenic Army General Staff, for the recovery of two missing soldiers from Lake Vouliagmeni in 1993. In 1996, Thoctarides was again recognised by the Hellenic Navy General Staff (HNGS) and Chief Vice-Admiral Paliogiorgos for his critical role in recovering the sunken PN 21 helicopter during the tense Greek-Turkish crisis at the Imia islets. That same year, he was honoured once more by Vice-Admiral Paliogiorgos for leading the search and recovery of the missing crew from the wreck of the P-25 KOSTAKOS torpedo boat.

Naval signal reporting the loss of the submarine HMS Trooper. Κ.Thoctarides archive, from research at the National Archives TNA.

His expertise has also earned him accolades beyond the military. In 2003, the Hellenic Ministry of Transport and Communications, along with the Air Accident Investigation and Aviation Safety Board, awarded him an honorary distinction at the 1st International Aviation Safety Conference for his vital contributions to recovering downed aircraft in Greek waters. His bravery was further acknowledged in 1997, when the International Academy of Letters and 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 his remarkable discovery and location of the HMS PERSEUS submarine off the coast of Kefalonia.

Not only is Kosta a pioneering figure in the realm of underwater exploration, but he is also an accomplished author and a producer of films and TV documentaries, specialising in the exploration and storytelling of 20th century historical shipwrecks.

The sinking of the submarine was due to an explosion of a German EMF-type mine containing 350 kg of hexane.

Relentless Pursuit

In more recent years, Kosta has continued his embrace of technology to push the boundaries of deeper wreck discoveries, utilising ROVs that can withstand the 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 chuckles. “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.

Despite the advanced technology, you might be surprised to learn that his scanning equipment largely consists of a modified, off-the-shelf fish-finder sonar, rather than specialised gear – definitive proof that skill and experience far outweigh the need for expensive gadgets.

OLYMPUS DIGITAL CAMERA

However, what truly sets him apart is his relentless passion. It drives him to conduct meticulous, multi-layered research, carefully piecing together historical records, eyewitness accounts, and his deep understanding of the sea. With every wreck he uncovers, Kosta experiences an exhilarating rush, driven by the thrill of revealing stories that only the physical evidence of a wreck can fully tell.

“In November 2021, I discovered the WWII Italian submarine Jantina, torpedoed by the British submarine HMS TORBAY on 5 July 1941. It was lying at a depth of 103 m (340 ft) 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.”

Underwater on 22.01.2020. Photo: Supplied

“You searched for three years?” I asked, astonished.

“Whenever I could, yes,” he said with calm determination. “It turned out 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 the crew had been taken completely by surprise by HMS TORBAY.”

“Persistence has to be the key to your success,” I remarked, impressed by his determination.

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

Kostas Thoctarides with his daughter Agapi at the helm. Photo: Supplied

I knew the story well – Kosta had eventually found spent torpedoes on the seafloor, which helped him discover the historically important wreck. Following the German invasion of Greece in April 1941 and the subsequent evacuation of British and Commonwealth forces, there was 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 the 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.

“Obviously research is a huge part of what you do. Has the internet helped you?” I asked.

“Only in a limited way, as most primary source materials are still archived only on paper. 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 1943 to a hero’s welcome – understandably.”

Underwater on 22.01.2020. Photo: Supplied

Kosta 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-degree turn.

“After the war,” he continued, “the captain of the ADRIAS, Ioannis Toumbas, was tasked with clearing the very same minefield that had crippled his ship. This is the chart from that minesweeping operation, and it eventually helped me locate the missing bow of the ADRIAS.” From his tone, the discovery was 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 moment the wreck was located, as recorded by sonar.

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 253 m (830 ft) 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.

Photo: Supplied

“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 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

What can one possibly say about a man who has seen and accomplished so much?

The submarine HMS Trooper (photo from the RN Submarine Museum Gosport file). Photo: Supplied

Reflecting on my conversation with Kosta, it became clear that his passion for uncovering maritime history runs far deeper than simply locating shipwrecks. His relentless dedication to research, his deep respect for those who perished at sea, and his unique ability to blend cutting-edge technology with old-fashioned detective work make him a true guardian of the past.

For Kosta, each discovery isn’t just about solving a mystery – it’s about preserving stories that might otherwise be lost to time. His work serves as a vital 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.

Photo: Supplied
  • Ross J. Robertson is an Advanced Open Water and Nitrox Diver, is an author and educator with a keen interest in Aegean shipwrecks and Greek WW2 history. Bringing these elements together in numerous magazine and newspaper articles, he is also the curator of the website ww2stories.org
  • Dr Konstantinos Giannakos is a retired Major (Infantry) with nearly 32 years of service in Greece and abroad. He holds a PhD from the University of Thessaly and has completed online seminars at the National and Kapodistrian University of Athens (EKPA) on Geopolitics and Security in the Middle East, as well as in electronic journalism related to Defense and Security. Currently, he writes for Military History magazine (Govostis Publications), the website SLpress.gr, and ww2stories.org, focusing on Anglo-Greek topics during WWII.

More photos below:

The characteristic cab bridge of the HMS TROOPER.
Right side of conning tower.
Right lower side of conning tower.
The platform of the periscopes, which are lowered and cannot be seen. On the left the antenna of the radar.
The stern of the submarine with the aft depth and heading rudders in the “mid” position. The port propeller is also visible.
The torpedo loading hatch on the fore deck. The loading crane with the steering wheel-shaped control and the ladder on the deck can be seen in the mounting position.
All underwater images have been supplied by Planet Blue – ROV Services. Founded in 1999 by award-winning Kostas Thoctarides, this leading enterprise offers expert solutions such as underwater observation, inspection, repair, maintenance, and installation support. Website: www.rovservices.gr
All underwater images have been supplied by Planet Blue – ROV Services. Founded in 1999 by award-winning Kostas Thoctarides, this leading enterprise offers expert solutions such as underwater observation, inspection, repair, maintenance, and installation support. Website: www.rovservices.gr
All underwater images have been supplied by Planet Blue – ROV Services. Founded in 1999 by award-winning Kostas Thoctarides, this leading enterprise offers expert solutions such as underwater observation, inspection, repair, maintenance, and installation support. Website: www.rovservices.gr
All underwater images have been supplied by Planet Blue – ROV Services. Founded in 1999 by award-winning Kostas Thoctarides, this leading enterprise offers expert solutions such as underwater observation, inspection, repair, maintenance, and installation support. Website: www.rovservices.gr
All underwater images have been supplied by Planet Blue – ROV Services. Founded in 1999 by award-winning Kostas Thoctarides, this leading enterprise offers expert solutions such as underwater observation, inspection, repair, maintenance, and installation support. Website: www.rovservices.gr
All underwater images have been supplied by Planet Blue – ROV Services. Founded in 1999 by award-winning Kostas Thoctarides, this leading enterprise offers expert solutions such as underwater observation, inspection, repair, maintenance, and installation support. Website: www.rovservices.gr
Ground zero where the explosion occurred is at frame 55, the blast wave swept through the crew’s accommodation compartment. Photo: Supplied
Sonar imaging of the wreck with Imaging Sonar at 525 khz the underwater ROV carries with it. 0. It is the center where the underwater vehicle carrying the sonar head is located. 1. The bow section has a total length of 29 meters. The break-in took place in frame 55 where the crew quarters were located. 2. Middle section – Conning Tower. The conning
tower has broken off at frame 98 at the point where the engine room watertight door is located. Total length 21,9 metres. 3. The stern section is the largest at 32.5 metres long. Photo: Supplied
The hatch of the conning tower is open and the engine room telegraphs can be seen on the left. Photo: Supplied
The D.F (Direction Funder FM4) is visible, a passive frequency locator, which provided the submarine with the ability to determine its position through mid-frequency transmissions (15 – 580 khz) by calculating its direction. Photo: Supplied
The inner door leading to the engine room is open. The midship section has broken off at frame 98 where the engine room watertight door is located. Photo: Supplied