Sources disagree slightly on the count, which is itself part of the story: her designed complement was 568 officers and men, while the figure most often given for the day she died is 597. The uncertainty exists because there were no survivors to muster and no bodies to bury. Whole engine-room watches, gun crews, signalmen, stokers, a wardroom of officers — all of them went down inside a hull that came apart before anyone on the upper deck could have understood what had happened.

Every one of them had a home port and a family waiting for news that would arrive as a list rather than a letter. In the Imperial Russian Navy of 1914, most were conscripted peasants and tradesmen serving out long enlistments a long way from where they were born. They are commemorated by nothing on the surface here. The water above them looks like any other stretch of the northern Baltic.

Pallada was the last of four armoured cruisers built for the Imperial Russian Navy in the first decade of the twentieth century — 449 feet long, 7,750 long tons, protected by Krupp armour 190 mm thick over her machinery, mounting eight-inch guns in turrets and a battery of six-inch guns in casemates. She was built at the Admiralty Shipyard in Saint Petersburg, begun in the summer of 1905, launched on 10 November 1906, and not completed until February 1911. Nearly six years from keel to commissioning is a long gestation, and it says something about a navy still reeling from the disasters of the Russo-Japanese War.

Her name carried that war with it. She was named for an earlier Pallada, captured by the Japanese at Port Arthur; both ships honoured Pallas Athena. She spent her entire career in the Baltic Fleet and never left it.

Six weeks before she died, Pallada did the single most consequential thing any Russian ship did in the Baltic. On 26 August 1914 the German light cruiser Magdeburg ran aground in fog off the island of Odensholm — now Osmussaar, Estonia — and could not be freed. Pallada and the cruiser Bogatyr came up and opened fire. The Germans destroyed the forward part of their own ship but failed to destroy their codebooks, and Russian boarding parties came away with copies of the Imperial Navy's signal book and the current cipher key.

One copy went to the British Admiralty in October 1914, where it gave Room 40 its first way into German naval wireless traffic. British codebreakers read the Kaiser's fleet for much of the war on the strength of it. Pallada was sunk before anyone aboard could have known any of that mattered.

U-26 did not long outlive her victim. Sometime around the end of August 1915 she disappeared in the Gulf of Finland, almost certainly mined, with all thirty of her crew. The exact date has never been fixed — 31 August and 4 September are both on the record. For a century she was simply gone.

Then Finnish divers found her in the western Gulf of Finland, and the discovery was reported in 2014. Both hulls now lie in the same shallow sea, a few dozen miles apart, and the men in both of them are still aboard. Whatever else these waters are, they are a war grave in two languages.

A Finnish diving group located Pallada outside Hanko in 2000 but kept the position quiet until 2012 — a decision that looks prudent in hindsight. She lies in three sections, all of them capsized, in roughly 40 to 50 metres of water. Silt has drifted over much of the wreck. One of her eight-inch turrets sits on the seabed beside the bow section, blown clear. Divers have photographed a large carved wooden Russian double-headed eagle still intact in the gloom, which is a strange thing to survive an explosion that killed six hundred people.

In 2013 came the report the divers had feared: the wreck, until then almost untouched, had been looted. In the Baltic's cold, low-salinity, near-anaerobic water, wood and metal can last for centuries. What such wrecks cannot survive is people with lift bags.