Bow of the Steuben Steering wheeel at bridge Sonar image of Steuben Map The team

Documenting the wreck of the Steuben was one of the biggest challenges Christoph Gerigk had ever faced. Although he had previously dived in a variety of hostile conditions, this adventure in the cold, green water of the Baltic Sea brought together most of the hazards a wreck diver could ever expect to encounter. At 50-71m, you could describe it as a moderate to deep trimix dive, but visibility was poor, the water was as dark as night (and 4-5ºC at depth), the wreck was shrouded with treacherous nets, surface conditions were turbulent and there was a permanent current coursing across the site. So why was a team of elite divers so determined to accompany Gerigk down to this eerie relic?

The Steuben was one of the last liners used to transport wounded German soldiers from the Russian front towards the end of the Second World War. Built in 1923, it was converted in 1944 to transport wounded soldiers; the refined trappings of a commercial liner were ripped out and the vessel was converted for use as a transport ship, complete with anti-aircraft guns. Steuben was thought to be carrying more than 5,000 soldiers and refugees when she was attacked in the Baltic Sea on 10 February 1945. Hit by two torpedoes from a Soviet submarine, she sank with the loss of an estimated 4,500 lives - more than three times the number of people who perished on the Titanic.

Pinpointed last year by the hydrographic office of the Polish Navy, the pressure was on to have a team of divers photograph the wreck in the 60th anniversary year of its sinking. Gerigk was commissioned by National Geographic to photograph the wreck, and the team - led by NG Poland's chief Marcin Jamkowski - chartered a fisheries research vessel for three weeks on the Baltic. In those three weeks they managed just five dives on the wreck, but were able to piece together a comprehensive picture of the wreck's final moments and its condition today.

'When the Steuben was attacked two torpedoes exploded in the crew's quarters, so there was virtually no crew to help the passengers escape on life rafts,' Gerigk says. 'Many of the people on board were wounded soldiers who couldn't run - some of them shot themselves when they realised they were effectively trapped. From the start, I knew that this wreck would have a sombre atmosphere, but it wasn't until we reached it that the full impact of its history was brought home.

'The wreck was lying on its port side: the highest point was at about 50m, and the lowest at 71m. Diving can be very easy in the Baltic, but it can also be very hard: it sounds crazy, but we put our kit on while still on the mother ship and were then towed to the buoy.' Conditions were far from ideal for technical diving - due to the ever-present current, the descent lines lay at a 30-degree angle, giving the divers a lengthy swim on the way down. 'It was warm on the surface, perhaps 18ºC,' Gerigk recalls. 'But by the time we descended below 30m, the temperature had dropped to 5ºC and it was even colder down on the wreck.' As one of the world's most versatile underwater photographers, Gerigk is used to taking his time underwater, using complex lighting techniques and trying out different approaches. Time was more pressing on this expedition: 'There was no time to experiment with photography or lighting - you go down, take the photographs and come back, preferably alive.'

When they finally neared the wreck after an exhausting descent, it was almost totally obscured with fishermen's nets. 'We couldn't see the ship at first, just layers and layers of nets - 60 years worth of them. We had a shot-line on the stern and started looking for a way past the nets. It was frightening, because we knew that the year before two divers had died on the Goya, another ship that lies in the Baltic which is also covered with fishing lines. Some of the nets hang in open water, held up by their buoys and moving around in the current. You never know where they are, but we used HID lights to try and keep track of them.'

The key to identifying the wreck lay in locating the torpedo hole. Normally, such a task would not present too many difficulties, but searching a 167m-long ship in total darkness - all the while negotiating shifting nets and a brisk current - was far from easy with a maximum bottom time of 25 minutes. 'In the end we found it almost by chance on the forward hull,' Gerigk says. 'There was a big gap, perhaps 3m high and 6m wide. We didn't go far inside because we had a limited bottom time. Also, there was a chance that there were bodies still inside and we didn't want to disturb this grave.'

It is thought that a torpedo went into the crew's quarters, exploded, then a second followed its route, creating a single big hole which is clearly visible on the Polish Navy's amazingly detailed sonar image of the wreck. Gerigk took a photo through the open hole, but kept to his decision not to venture significantly inside the wreck.

His team included his German assistant Steffen Scholz, plus trimix divers from Poland and the Czech Republic, whose job it was to secure a shot-line to whatever part of the wreck Gerigk needed to photograph. The full length of the wreck was marked out by buoys, including marks for the stern, bridge and bow areas.

'The main challenge was carrying out a technical-diving operation together with underwater photography,' Gerigk says. 'Everybody had to carry about 200lbs [90kg] of equipment: I had twin 20s on my back, plus stage cylinders, a big camera and various tools. The support divers would go down and put a line on the wreck. The photographic team would follow, do the photography, then go back up. For each dive, we were in the water for about two and a half hours. Decompression was not too bad, because the water was warm close to the surface. For each dive, we were in the water for about two and a half hours.'

For Gerigk, diving on the Steuben had a personal resonance. During the Second World War, his family were living in a town near Danzig (now Gdansk) and had a ticket for the Wilhelm Gustloff, another transport ship that was sunk by the same Soviet submarine. It was winter, and his grandmother had put the children's boots on top of an oven to dry them. She left them there too long, so when the time came to leave, they couldn't fit into their own baked footwear. 'They missed the voyage, but leaving those boots on the oven probably saved their lives,' Gerigk says. 'I wouldn't be here if they hadn't shrunk their shoes!' Five dives in three weeks were sufficient for Gerigk to record the Steuben's key features and attune to its melancholy atmosphere. He entered the wreck on just one occasion, a tentative foray into the wheelhouse, which he carried out towards the end of a dive, closely watched by technical diver Steffen Scholz, who worked as Gerigk's lighting assistant. 'Just before, I had got myself hooked on a piece of net, and it took me several minutes to free myself. It doesn't sound like much, but it was a significant portion of my bottom time. I took a photograph and a minute later I entered the wheelhouse. I had previously spoken to the last person to escape from the bridge, and from what he'd told me it was unlikely there were any bodies there.

'When you dive a wreck you feel the soul of a ship. You're not just diving on a pointless object - you feel it. In the case of Steuben, the atmosphere was oppressive. Sure, it's an adventure and a privilege to be there, but you could never call it a delightful dive. It's a downbeat experience, and the presence of those nets with the trapped and decaying fish makes it all the more foreboding. For me, Steuben is a ship of ghosts.'

The sinking

Steuben was sunk by Captain Alexander Marinesko of the Soviet submarine S-13 on 10 February 1945. The ship had left the port of Pillau (now Baltiysk) and was heading west when Marinesko spotted the glowing smokestacks of the refugee ship's escorts. After tailing Steuben for four hours, he fired two torpedoes and the ship went down. Only 659 people were rescued from the near-freezing water; it is estimated that 4,500 perished on board Steuben.

Marinesko had already sunk another transport ship, Wilhelm Gustloff and he was awarded the Combat Order of the Red Banner for his record in sinking the most tonnage in a single cruise (an estimated 40,000 tonnes). His glory was to be short-lived: insubordinate conduct on shore offended his superiors and he was discharged after the war.

Photography in a cold climate

Gerigk used a Nikon F5 film camera in a Seacam housing to photograph the Steuben. In the absence of any natural light, he used a combination of light from four movie-style HID lamps made by Treble Light and a selection of powerful Subtronic flashguns, which penetrated the murky water to distances of up to 3m. He also used HID lights as a 'working light' so that he could see what he was shooting and to keep an eye out for the ubiquitous fishing nets. He also used a Seacam-housed Nikon D1X digital camera on the first dive to preview photographic conditions, but was adamant that the main body of wreck images should be shot on film.