Spain’s newest submarine was 75+ tons heavier than expected because someone put a decimal point in the wrong place. It could go down, but might not come up again.
The US Navy has a tradition that no submarine is ever considered lost at sea. Subs that don’t return, including 52 lost during WWII, are considered “still on patrol.” Every year at Christmastime sailors manning communications hubs send holiday greetings to those listed as still on patrol.
In the whole history of submarine warfare, there was only ever one underwater submarine battle. That battle was also the only time a submerged submarine sunk another submerged submarine.
In 1900, when submarines were being introduced to navies, Admiral Arthur Wilson called them underhanded, threatening to hang enemy sub crews as pirates. So, in 1914, when Max Horton commanded Britain’s first sub engagement against the Germans, he ordered his crew to fly a Jolly Roger.
The first combat submarine to sink a warship also simultaneously sank itself.
HMS Thetis has the rare and unwanted honor of a submarine to have twice sunk and killed her crew. She sank during trials in 1939, drowning 99 men, before being raised and renamed. Sunk again during battle in 1943, her entire second crew was also lost.
A tool shop owner paid $100 for a locked abandoned storage unit, only to find the Lotus Esprit submarine prop from The Spy Who Loved Me inside. He sold it to Elon Musk for $825,000.
During World War 2, Allied submarines would lie on beds of pistol shrimp. The snapping sound made by the shrimp was so loud, it stopped the submarines from being picked up on Japanese sonar.
In 1961 Donald Reid built a Flying Submarine. It was demonstrated on 9 June 1964 where it dove to a depth of 6.5 feet (2 m) then flew to an altitude of 33 ft (10 m).
Four submarines from various nations around the world were all lost a few months apart in 1968. None of the losses were ever explained.