I understand perfectly.

3 seconds sound clip from the The High and the Mighty (1954) movie soundboard.

You can hear this line at 00:31:10 in the DVD version of the movie.

Quote context

[...]

- I've got a lovely wife and two kids, another on the way. I wouldn't be doing this if I didn't think it was safe.

- You hedged, Captain. You didn't answer my question.

- Come now, be a good honest fellow and tell me exactly what frightened you?

- Well, well, they were technical incidents.

- I don't think you'd understand, Mr. Pardee.

- I understand perfectly.

- For some reason, you were afraid you wouldn't reach your biblical span of life.

- Which is precisely what's bothering me at the moment.

- I'm convinced I couldn't swim from here to the nearest shore.

- You won't have to swim, Mr. Pardee.

[...]