NBM Dive Site Resource
SM UB-21 — Solent scattered remains
Spithead, Portsmouth and the Isle of Wight, United Kingdom coastal waters, United Kingdom
Maritime Archaeology Trust combined National Archives documents with diver surveys to identify UB-21’s dispersed Solent remains.
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Featured Hero Photograph
Aquatic life at this dive site
What divers may encounter
Three reviewed connections are featured here. Sightings vary by season, conditions, and chance, so they are never guaranteed.
Aquatic life research in progress
NBM is reviewing a likely local species for this position.
Aquatic life research in progress
NBM is reviewing a likely local species for this position.
Aquatic life research in progress
NBM is reviewing a likely local species for this position.
Site media
Photographs
Three views rotate from the published gallery on each visit.
Contributor media
Dive videos
Three featured video positions are reserved on every profile.Regional location and nearby land
Location map
Regional view includes nearby land for orientation. Historical loss reports are not navigation fixes; no precise wreck position is inferred.Map data © OpenStreetMap contributors
Recent field observations
Diver-reported temperatures
Automatically checked observations from dives during the past 14 days. Three reports are visible at a time; scroll for more.A report that passes the automatic checks will appear here with the dive date, diver’s display name, and temperatures at each depth.
Reports are automatically checked for plausible dates, depths, and temperatures. They are observations, not forecasts; confirm conditions before diving.
Why divers know this place
Highlights
Maritime Archaeology Trust combined National Archives documents with diver surveys to identify UB-21’s dispersed Solent remains.
Shipwreck-only module
The wreck
This section appears only on shipwreck records and brings the vessel, its loss, present condition, access, and responsible wreck-diving considerations into one place.
- Vessel type
- German World War I Type UB II submarine
- Year built
- 1915 (launched)
- Year sunk
- 1920
- Cause of loss
- Sunk by HMS Terror during gunnery trials on Horse Tail Sands off Portsmouth on 20 September 1920, then demolished and swept.
- Present condition
- Widely dispersed hull, machinery and fitting fragments after gunnery trials, demolition and sweeping; not an intact submarine.
- Penetration guidance
- External historical context only; no authorization for penetration, recovery or disturbance.
Before you arrive
Access notes
The Trust’s archival evidence gives 20 September, correcting the 30 September date in the specialist summary. The shallow 4–10 m site contains scattered remains, not an intact submarine; the Bailey’s Brow wreck is a different boat. This record documents a wreck and its research history. It does not establish public charter availability or permission to visit. Confirm access with the responsible authorities and qualified local support; respect the site’s naval-heritage context.
Plan within your training
Conditions and hazards
Offshore weather and currents, depth and decompression exposure where applicable, low or changing visibility, entanglement, unstable or damaged metal and possible ordnance. Do not disturb remains or remove objects.
Independent resource notice
This record is a starting point for independent verification. Access, closures, moorings, weather, currents, depth, visibility, operator availability, and site conditions can change without notice. Confirm current information with the responsible operator, property owner, managing authority, or another qualified local source before planning or attempting a dive.