Vanguard

The Vanguard was the victim of an internal explosion. Her magazine was detonated by unstable cordite and within seconds the battleship was annihilated together with all but three of her 800 crew and officers. One of her 12 inch turrets was thrown over a mile to land in Flotta. This appalling accident happened in July 1917. In some ways it resembled the explosion that the cruiser HMS Natal suffered in Cromaty Firth in 1915, and for some time sabotage was suspected.

She was built at Barrow and completed in 1910. She was one of the earlier descendants of the original Dreadnought and was a powerful warship to start with. HMS Vanguard displaced nearly 20000 tons and was 536 feet long. Her armament was substantial. It included 5 gun turrets each with two 12 inch guns, twelve 4 inch guns and three 18 inch torpedo tubes. Her turbines were powerful. She spent much of her time in WW1 at Scapa Flow, with the odd sortie across the North Sea. She saw action at Jutland, but came out without damage.

The Vanguard - or what's left of her - lies in 34 metres just north of Flotta. In the 1960's and 70's some salvage was carried out on her, but since 1982 she was declared a war grave. It is expressly forbidden to dive within 100 metres of her. Apparently, there is much wreckage, live ammunition, capstans and so forth that are littering the sea bed. The bows still stand intact and are the final  resting place of some of those 800 people who perished with her.

References.

MacDonald, Rod "Dive Scapa Flow" Mainstream Publishing 1998
ISBN 1 85158 983 X