Better breathe your oxygen, just in case.

4 seconds sound clip from the The Atomic Submarine movie soundboard.

You can hear this line at 00:49:59 in the DVD version of the movie.

Quote context

[...]

- Ready to open air lock door, Captain.

- Go ahead, Griff.

- What now?

- What do you say, Doctor? Shall we take a chance?

- That's what we came for.

- You all stay here. I'm gonna take a look inside.

- Not alone, you're not.

- Better breathe your oxygen, just in case.

(Submarine sliding door)

- Air, pure air, under pressure.

- That's a relief.

- Well, we won't need these tanks.

- Good luck, men.

- All right, let's go.

[...]