U-1206 had short and somewhat ignominious service life. This type of U-Boat was equipped with a new type of toilet designed to allow the submarine to dive deeper and avoid Allied attack. It was a very complicated high-pressure valve system which required special training to use them. It led to the disastrous end of U-1206.

The submarine departed from Karljohansvern, Norway for a one-day patrol on 2 April 1945; its first (and only) active patrol began on 6 April when it departed from Kristiansand. On 14 April, while U-1206 was cruising at a depth of 200 feet (61 m), 8 nautical miles (15 km; 9.2 mi) off Peterhead, Scotland, misuse of the new toilet caused large amounts of water to flood the boat. According to the commander's official report, while in the engine room helping to repair one of the diesel engines, he was informed that a malfunction involving the toilet caused a leak in the forward section. The leak flooded the submarine's batteries (located beneath the toilet) causing them to release chlorine gas, leaving him with no alternative but to surface. Once surfaced, U-1206 was discovered and bombed by British patrols, prompting the commander to scuttle the submarine. One man died in the attack, three men drowned in the heavy seas after abandoning the vessel and 46 were captured.

More Info: en.wikipedia.org