German submarine U-1206 sank itself in 1945 after a malfunctioning high-pressure toilet allowed seawater into the boat.
U-1206 was a late-war Type VIIC submarine operating near Scotland in April 1945. Its advanced toilet system was designed to work at diving depth, but it required specially trained technicians. When the system malfunctioned, a plumber was called to inspect it. An incorrect valve operation allowed seawater to enter the pressure hull and caused problems with the battery compartment.
The resulting chlorine gas threat forced the submarine to surface. British aircraft attacked the boat, and its commander, Karl-Adolf Schlewe, ordered the crew to abandon and scuttle it. Several crew members were captured, while others reached the shore or were lost.
U-1206 is often remembered as the “toilet submarine,” but the toilet did not simply sink the boat by itself. The technical failure led to flooding, hazardous fumes, surfacing, and the subsequent air attack.