SMS Markgraf

Markgraf fought at Jutland and now lies almost fully inverted in the deepest water of the German fleet, her upturned hull rising from around 45 m to the mid-twenties. The scale registers slowly: a wall of riveted plate longer than a football pitch, rudders raised toward the light, and along the port side the crushed gallery where casemate guns and portholes emerge from the shadows. This is a dive of atmosphere rather than easy sightseeing — dark, deep and unforgiving of poor planning — and for many wreck divers it is the single best thing in British waters.

The moment you come for: Dreadnought scale in the gloom, casemate guns along the hull side, the fleet's most prestigious tick

Topography: A Konig-class battleship lying nearly upside down on a silt-and-shell seabed at about 45 m

Entry: Shotline descent from Stromness charter boats; the deepest and most demanding of the German fleet.

Hazards: Depth, darkness, silt and inverted orientation that disorients; penetration is a technical-team undertaking only.

Conservation: A scheduled monument: nothing is removed, nothing disturbed. A century of salvage history already scars the fleet — divers should not add to it.

Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).