U-Boat SM UC-77 (1918)
SM UC-77 wreck dive
The SM UC-77 wreck dive explores the story of a German Type UC II minelaying submarine lost during the final year of the First World War. UC-77 operated from Flanders and attacked Allied shipping with torpedoes, gunfire and mines. Therefore, this SM UC-77 wreck dive links the Dover Strait directly to the wider U-boat campaign.
UC-77 had already built a serious record before her final patrol. Uboat.net credits her with 35 ships sunk and 7 damaged across 13 patrols. However, in July 1918, she tried to pass through the Dover Barrage and failed to return.
SM UC-77 wreck dive: the submarine before the loss
AG Vulcan built UC-77 at Hamburg as yard number 82. The German Navy ordered her on 12 January 1916, launched her on 2 December 1916 and commissioned her on 29 December 1916. She first served under Kapitänleutnant Reinhart von Rabenau, then under Oberleutnant zur See Johannes Ries.
She belonged to the Type UC II class, a group of German minelaying submarines designed for offensive work in busy waters. UC-77 measured about 50.45 m overall and displaced about 410 tonnes on the surface. In addition, she carried torpedoes, a deck gun and 18 UC 200 mines.
That mine-carrying role made boats like UC-77 especially dangerous. They could attack a ship directly, then leave mines in shipping lanes for later victims. As a result, one patrol could create risk long after the submarine had left the area.
The Dover Barrage and final patrol
By 1918, UC-77 operated with the Flandern flotillas from the Belgian coast. These boats targeted the Channel, the North Sea approaches and Allied traffic moving around Britain and France. Meanwhile, the British strengthened the Dover Barrage to block U-boats from passing through the Strait.
UC-77 left for her final patrol in July 1918. Historic England records that she was outward-bound from Zeebrugge for operations off Portland and the Owers. However, she never reached that patrol area.
The Dover Barrage account states that UC-77 dived while trying to pass through the defences, but she left bubbles and leaking oil on the surface. The British drifters Kessingland and Golden Grain spotted the trail and attacked with depth charges. Then, because UC-77 carried mines, the explosions appear to have detonated some of her own ordnance.
The exact loss position remains disputed. Some records place the loss in the Dover Strait or off Folkestone, while others refer to the Flanders coast or Fairy Bank. Therefore, the safest wording is that UC-77 was lost during an attempted outward passage through the Dover Barrage in July 1918.
You can read the vessel and patrol summary in Uboat.net’s UC-77 record. The Kent wreck record and loss-position discussion appear in Historic England’s UC-77 entry.
The wreck today
For divers, UC-77 offers a powerful First World War submarine story with genuine historical tension. She was not a passive casualty. She had sunk or damaged dozens of vessels before her own final encounter with the Dover defences.
All 30 men aboard died, including Oberleutnant zur See Johannes Ries. I have not found a complete reliable open list of the crew in the accessible sources, so the event page should avoid naming men beyond those confirmed by reliable records. Even so, the casualty figure gives the wreck clear war-grave weight.
The dive also gives context to the Dover Strait itself. This was not an empty stretch of water between England and France. It was a defended, mined, patrolled and contested choke point. UC-77 reminds us that the seabed off Kent still holds the hard evidence of that fight.
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