Why Are Submarines Undetectable?

A submarine can “hide” under a layer of cold water where an active hull-mounted sonar (HMS) can't reach since the sound wave will bounce off the layer up against the surface. For this reason, surface ships

have variable depth sonars (VDS) that they can dip below the layers and search.

What makes submarines undetectable?

How do the subs get so stealthy? Ballistic-missile submarines are built to evade detection by making as little noise as possible. They move slowly—usually no more than 20 knots. They're coated in anechoic tile, a rubbery substance that absorbs sound and prevents sonar detection.

How do submarines not hit anything?

Submarines carry an inertial navigation system, which measures the boat's motion and constantly updates position. ... To maintain accuracy, the submarine must periodically update its position using outside navigational radio signals.