Reason for Loss: Damaged by mine and sunk by collision
On 2nd December 1917, SM UB-81 was patrolling south of the Isle of Wight when it hit a mine and sank. The rear of the submarine was badly damaged, but by pumping air into the forward tanks, the crew managed to get the bow of the vessel clear of the water. By removing a loaded torpedo, several men were able to crawl up the torpedo tube and escape. Conditions outside were so unpleasant that several of the crew returned inside saying they would rather die below than freeze outside. The Royal Navy patrol vessel HMS P32 came alongside to assist, but hit the bow of the U-boat. Water poured into the torpedo tube and the submarine sank, drowning the remaining men on board.
Historic sources paint different pictures of the loss. Although the log book of HMS P32 makes no mention of the collision, German survivors repeatedly suggests the patrol boat rammed the U-boat.
Today the remains of SM UB-81 lie in nearly 30m of water south of Portsmouth. It is designated as a Controlled Site under the Protection of Military Remains Act - making it illegal to dive on the site.