The reason submarines can detect other underwater objects is largely due to?

Question

The reason submarines can detect other underwater objects is largely due to?

Answer 1

The greater capacity for water to carry sound waves when compared to air.

That's why you don't tap the fish tank glass.

Answer 2

Passive sonar, which is a series of transducers mounted in key places in the hull. The transducers pick up sound and transmit it to the sonar technician and display it on his console.

Sound conducts better through water than through air.

Most of it is classified, but you get the idea.