CAIRNMONA - Scapa Flow, Orkney

The Cairnmona sits upright, broken into three main sections, a casualty of a U-boat torpedo in 1939. We love how accessible this wreck feels despite its 50-meter depth, making it a proper technical dive without the usual faff of an overturned or completely flattened vessel. Dropping down onto her bow, you’re greeted by the sheer scale of it, and we always make a point to explore the intact forward holds. The midsection is where she took the hit, and it’s a chaotic but fascinating jumble of twisted metal, home to a surprising amount of invertebrate life – we’ve seen some huge plumose anemones here. Our favourite part has to be the stern, relatively intact with the propeller still in place, often obscured by schools of saithe that swirl in the low light. The engine room is penetrable, a dark, silty delve for the properly trained, but even from the outside, the triple-expansion engine is a grand sight. Visibility in Scapa can vary wildly, but on a good day, the silhouette of the Cairnmona against the green gloom is genuinely evocative. It’s a cold dive, so drysuits are essential, and we’d suggest opting for a late summer or early autumn trip for the calmer surface conditions. This wreck suits experienced technical divers keen on exploring a significant piece of wartime history, a place where the past feels tangible.

Location
Scapa Flow, Orkney, United Kingdom, Mediterranean & Europe
Coordinates
57.629400, -1.729717
Type
wreck
Maximum Depth
50m

Wreck History - CAIRNMONA

Year Sunk
1939
Vessel Type
cargo ship
Cause
torpedo

Built in 1918 towards the end of the First World War, the SS Cairnmona was a classic steamship powered by a triple-expansion engine. Owned by the Cairn Line, she served as a merchant vessel for two decades before being called into service at the dawn of the Second World War. Her story is deeply intertwined with the strategic importance of Scapa Flow, the Royal Navy's primary base in the north.

On October 30, 1939, just weeks after the war began, the Cairnmona's fate was sealed. While in the waters of Scapa Flow, she was targeted by the German submarine U-13. A torpedo strike sent the vessel to the bottom, making her one of the early merchant casualties in these historic and heavily defended waters. Her sinking was a stark reminder of the U-boat peril that lurked just outside the main naval anchorage.

Today, the Cairnmona rests at a depth of 50 meters, placing her firmly in the realm of technical diving. This is a challenging dive for experienced, properly equipped divers. The cold, dark waters have preserved her structure remarkably well, though the explosive torpedo damage is evident. Exploring this WWI-era vessel offers a poignant and atmospheric connection to the opening salvos of the Battle of the Atlantic.

Marine Protected Area: Loch of Strathbeg

Best Time to Dive in Scapa Flow, Orkney

The warmest water temperatures in Scapa Flow, Orkney occur in January, averaging 8.4°C. The coolest conditions are in December at 8.4°C.

Monthly Water Temperatures

  • January: 8.4°C (air: 5.5°C)
  • February: 8.4°C (air: 5.3°C)
  • March: 8.4°C (air: 5.9°C)
  • April: 8.4°C (air: 6.8°C)
  • May: 8.4°C (air: 9.7°C)
  • June: 8.4°C (air: 12.4°C)
  • July: 8.4°C (air: 13.2°C)
  • August: 8.4°C (air: 13.7°C)
  • September: 8.4°C (air: 12.7°C)
  • October: 8.4°C (air: 10.2°C)
  • November: 8.4°C (air: 8.0°C)
  • December: 8.4°C (air: 5.8°C)

Nearby Dive Sites in Scapa Flow, Orkney

Nearest Dive Centres to CAIRNMONA

Marine Life in Scapa Flow, Orkney

Home to 155 recorded species including 63 reef fish, 17 whales & dolphins, 12 sharks & rays, 11 crabs & lobsters, 11 other, 10 seagrass & algae.

Notable Species

Recommended Packing List for CAIRNMONA

Based on average water temperature of 8.4°C.

  • Drysuit - water at 8°C demands a drysuit with thermal undergarments
  • Hood & Gloves (7mm+) - critical to prevent heat loss
  • Mask - essential for every dive
  • Fins
  • BCD - buoyancy compensator
  • Regulator - your most safety-critical piece of gear
  • Dive Computer - tracks depth, time, and NDL
  • Surface Marker Buoy (SMB) - essential for boat pickups
  • Dive Torch - useful for crevices and colour at depth
  • Underwater Camera - capture your diving memories