Scapa Flow

Diving works off hard boats out of Stromness, with some charters based in Kirkwall. Most carry a lift, an onboard compressor and bunks, so groups often live aboard for the week rather than book a hotel. The pattern is two dives a day, the deeper one first and something shallower after a long surface interval. Skippers shot the wreck, brief it on the run out, and set the order from tide tables and forecast rather than a fixed weekly schedule. Nitrox is widely available and many regulars dive twinsets or rebreathers.

The ships read very differently depending on how they landed. The three surviving battleships are all König class, and all capsized as they sank, so what you swim is an inverted hull with the armour belt and casemate guns emerging along the flanks: impressive, but hard to make sense of without a guide or several repeat visits. The cruisers settled onto their sides, which leaves decks, gun mounts and rangefinders legible. Salvage crews worked the fleet for decades, mostly between the wars, and the cutting and blasting they left behind is much of what you now swim through.

The Flow's other layer is defensive rather than German. The eastern sounds were closed with sunken blockships and then sealed by the Churchill Barriers, built largely with Italian prisoner-of-war labour after Royal Oak was lost. What sits in Burra Sound lies in hard tidal flow: shallow and straightforward once you are in, dived only in the short slack, and usually the clearest water on the roster. HMS Royal Oak, torpedoed at anchor in October 1939, is a protected war grave and closed to sport diving. Carry a proper torch, because even at midsummer the hulls sit in their own shadow.

This suits divers who came for history and are content with dark water and a great deal of steel. On the battleships the upturned keel sits around 20 m, but the armour belt and guns are down at the seabed, so the detail is the deep part of the dive; the cruisers and the shallow blockships are the forgiving end of the roster. Orkney absorbs weather days well, with Skara Brae, Maeshowe and the Ring of Brodgar a short drive from Stromness, and long northern daylight keeps the summer pace unhurried. Divers after reef life will find little of it.