U-133 was a Type VIIC submarine, the workhorse of the German Kriegsmarine's submarine fleet during the Second World War. She was laid down at Vegesacker Werft in Bremen-Vegesack on 21 August 1940, launched on 28 April 1941, and commissioned into service on 5 July 1941. The Type VIIC was a capable and numerous class: at 67.10 metres in length, displacing 769 tonnes surfaced and 871 tonnes submerged, these boats could operate to depths of 230 metres and travel 8,500 nautical miles on the surface at economical speed. U-133 carried five torpedo tubes — four at the bow and one at the stern — fourteen torpedoes, and a deck gun. Her crew numbered 45 men. She was, in the language of the era, a fighting boat. In March 1942, she was operating in the waters around Greece, in a war that had by then spread across every sea.

The Saronic Gulf, the body of water that curves around Athens and its surrounding coast, was heavily mined during the Second World War. Mines were laid by multiple parties — German, Greek, and Allied forces all seeded these waters. U-133 encountered one of these mines on 14 March 1942, near Aegina island; evidence suggests the mine may have been German, possibly because the boat strayed from its programmed route. The submarine left her base at Salamina at 17:00 that evening and sank within two hours. A mine strike gave no time for escape. The pressure wave of the explosion could destroy a pressure hull instantly; the sea flooded in faster than any crew could respond. There was no distress signal, no time for the men to get clear. The boat went down, and the crew — every one of them — went with her. In submarine warfare, this was not unusual. It was one of many such losses across many seas. But each boat that went down took with it the particular lives of the men aboard, their names, their histories, the people who were waiting for them.

For more than four decades, U-133 lay unrecorded on the seabed. In 1986, two professional divers — Efstathios "Stathis" Baramatis and Theofilos Klimis — came across a submarine wreck by chance at a depth of 78 metres. They identified it as an unknown German submarine but could not immediately determine which boat it was. Almost ten years later, in the mid-1990s, Greek divers made a further identification: this was U-133. The wreck has remained on the seabed of the Saronic Gulf since. At that depth, in those waters, the boat is accessible to technical divers but lies well beyond recreational diving limits — a cold, dim place where the hull has been slowly claimed by marine growth and time. It is a war grave.

The Saronic Gulf does not memorialize U-133. There is no marker above the water, no ceremony, no monument on the shore of Aegina to record what happened there in March 1942. The men who died were German sailors fighting for a regime that had invaded the country beneath whose waters they now lie. History offers no simple framing for this. They were young men — most submarine crews were young — who had been trained for a dangerous profession in a terrible war, and they died doing it. The boat and its crew are part of the Saronic Gulf's layered history of conflict, which stretches back to the Battle of Salamis in 480 BC. The war moved on. The wreck stayed.