Submarine · 1916–1917 · Cork, Ireland
SM UC-42
Also known as UC-42, UC42, U-boat UC-42.
SM UC-42 is a German submarine built in 1916 and destroyed by one of her own mines in 1917; the wreck lies at 25–30 metres off Cork, Ireland. The site is a designated war grave.
The crew of UC-42 were laying mines to destroy other ships when one of their own mines destroyed them. On 10 September 1917, this German UC II-class minelaying submarine was deploying a minefield at the entrance to Cork Harbour off Roches Point when a mine detonated, killing all 27 crew instantly.
The wreck was relocated by divers in 2010 in approximately 28-30 metres and subsequently designated a war grave under the National Monuments Acts. She rests on her port side with the keel visible and an external bow torpedo tube lying in the silt beneath.
In 2024, divers from Blackwater Sub Aqua Club and Mizen Archaeology recovered one of the propellers after months of careful excavation -- a significant maritime heritage event covered by RTE and the Irish Examiner. A licence under the National Monuments Acts is required to dive this protected site.
- Type
- SubmarineGerman
- Year built
- 1916AG Vulcan, Hamburg
- Lost
- September 10th, 1917Mine (own)
- Casualties
- 27World War I
- Tonnage
- 434 GRTdiesel-electric
- Length
- 49.4 m5.2 m beam
- Depth
- 25–30 m
- Location
- Cork, IrelandCeltic Sea
4 of 8 facts above are cited in Sources below.
Deeper than 88 of the 185 wrecks on the map with a recorded depth.
- Position: Published positions differ between sources; the position shown follows the position policy. Other published figures exist (why sources disagree).
History and LossLost September 10th, 1917 · Mine (own) · World War I · Cork, Ireland.
Sent to sow mines across the approaches to Cork Harbour, one of Ireland's busiest ports, UC-42 was at work off the harbour mouth on 10 September 1917 when one of her own mines went off. The blast destroyed the submarine and killed all 27 men aboard in an instant. UC-class boats were known to be at risk from their own mines, and several were lost that way during the war.
Built 1916 by AG Vulcan, Hamburg; 1 years in service, also recorded as UC-42 and UC42 and U-boat UC-42. Lost September 10th, 1917, mine (own) during World War I.
The Voyage
- Cargo
- UC II-class minelaying submarine carrying mines
Condition of the WreckLargely intact, in 25–30 m, on sand and mud.
Intactness
Resting on port side. Keel visible. Hull largely intact but deteriorating after 100+ years. External bow torpedo tube displaced into silt beneath keel.
One propeller was recovered by divers in 2024. The wreck site is automatically protected under the National Monuments Acts 1987-2014.
Notable Features
- Rests on port side with keel visible
- External bow torpedo tube in silt beneath keel
- Propeller recovered 2024 by Blackwater Sub Aqua Club
- Designated war grave
Regulations and RestrictionsWar grave.
This is a war grave, where human remains may be present. Protected wreck (over 100 years old) under the National Monuments Acts (National Monuments Service).
War grave - no disturbance permitted.
Additional Details16 further fields held for this wreck and not shown above.
- Nationality
- German
- Flag
- Germany
- Builder
- AG Vulcan, Hamburg
- Propulsion
- Diesel-electric
- Loss date
- September 10th, 1917
- Conflict / event
- World War I
- Latitude
- 51.77° N
- Longitude
- 8.25° W
- Water body
- Celtic Sea
- Protection regime
- Protected automatically under the National Monuments Acts 1930-2014: all wrecks over 100 years old in Irish waters are protected, and underwater archaeological objects are protected irrespective of age.
- Artefact restrictions
- War grave - no disturbance permitted
- War grave
- Yes
- Protected
- No
- Permit required
- No
- Condition
- Largely intact
- Seabed
- Sand and mud
Sources and VerificationEvery cited fact on this page traces to a published source.
- irishtimes.comirishtimes.com · Secondary source6 facts
- Wrecksitewrecksite.uk · Secondary source6 facts
- dusac.orgdusac.org · Secondary source5 facts
- rte.ierte.ie · Secondary source3 facts
- Afloat.ieafloat.ie · Secondary source2 facts
- Irish Wrecks Onlineirishwrecksonline.net · Secondary source2 facts
- Divernetdivernet.com · Club or operator4 facts
- Wikipediaen.wikipedia.org · Background reading10 facts
Background reading is listed for context and is not counted as a citation for the facts above.
A further 4 fields were derived from the wreck’s recorded position rather than taken from a source.
Licences and credits for the open data used on this site are on the Attribution page.
Frequently Asked Questions
What is the SM UC-42?
SM UC-42 is the wreck of a submarine, off Cork, Ireland, at 30 metres. SM UC-42 was destroyed by one of her own mines in 1917.
How deep is the SM UC-42?
SM UC-42 lies at 25 to 30 metres, Approximately 5 nautical miles south of Roches Point, Cork Harbour.
How did the SM UC-42 sink?
SM UC-42 was destroyed by one of her own mines on September 10th, 1917 during World War I, off Cork, Ireland. 27 people lost their lives.
Is the SM UC-42 protected?
Yes. SM UC-42 is protected: protected wreck (over 100 years old) under the National Monuments Acts (National Monuments Service). SM UC-42 is recorded as a war grave.