It's completely waterproof and actually plastic. See? You can do what you like with it.
6 seconds sound clip from the The Bridge on the River Kwai movie soundboard.
You can hear this line at 01:21:05.203 in the Blu-ray version of the movie.
Quote context
[...]
- Fascinating place, isn't it?
- Utterly charming. I didn't realise it was a commando school.
- We're trying to discourage that word. It has such a melodramatic air about it.
- Oh, sabotage, demolition, that line of country.
- It's quite harmless until it's detonated.
- It's completely waterproof and actually plastic. See? You can do what you like with it.
- Oh, I'm dying for a cup of tea. Would you care for one?
- A drink?
- Pot of tea for one, please, Peter.
- Oh, I taught Oriental languages at Cambridge before the war.
[...]