The islands surrounding Scapa Flow made one of Britain's best natural harbours, while the location at the north of Scotland protected the approaches to the North Sea and Atlantic. The naval base was important during both wars but what makes Scapa Flow famous is its wrecks, the remains of a German fleet, which once numbered some 74 vessels, most of which were scuttled in 1919, as well as the war graves of HMS Royal Oak and HMS Vanguard. The wrecks of the navy ships still survive, along with eight German warships for which a second war came and prevented salvage. Now a divers' paradise, the...