What was the cause of the USS Squalus sinking in 1939?

The USS Squalus sank primarily due to a valve failure, specifically related to the main induction valve. During a test dive off the coast of New Hampshire in May 1939, the main induction valve, which is responsible for allowing seawater to enter the submarine's ballast tanks to ensure it could dive, failed to close properly. This failure allowed water to flood the submarine unexpectedly, leading to its sinking.

Understanding the operation of valves in submarines is critical, as their proper functioning directly affects a submarine's safety and ability to dive and surface efficiently. When the valve malfunctioned, the crew was unable to recover from the flooding, which ultimately led to the disaster. This incident prompted significant changes to submarine design and safety regulations, emphasizing the need for reliability in vital systems like valves.