- Like how quiet?
- It's doubtful our sonar'd even pick it up, and if it did, it'd sound like whales humping or some kind of seismic anomaly, anything but a submarine.

11 seconds sound clip from the The Hunt for Red October movie soundboard.

You can hear this line at 00:22:03.728 in the Blu-ray version of the movie.

Quote context

[...]

- How about a towed sonar array?

- Nope. Too close to the screws.

- I'll be... This this could be a caterpillar.

- A what?

- A caterpillar drive. Magneto-hydrodynamic propulsion.

- You follow?

- No.

- It's like a jet engine for the water... goes in the front, gets squirted out the back only it's got no moving parts, so it's very, very quiet.

- Like how quiet?

- It's doubtful our sonar'd even pick it up, and if it did, it'd sound like whales humping or some kind of seismic anomaly, anything but a submarine.

- We messed with this a couple of years ago. We couldn't make it work.

- They really built this? This isn't a mock-up or anything?

- She put to sea this morning.

- When I was 12, I helped my daddy build a bomb shelter in our basement because some fool parked a dozen warheads 90 miles off the coast of Florida.

[...]