Over hundreds of years, perhaps over thousands of years, the current would break it up.
4 seconds sound clip from the Creature from the Black Lagoon (1954) movie soundboard.
You can hear this line at 00:17:16.252 in the Blu-ray version of the movie.
Quote context
[...]
- Had enough, Mark, or do we keep on digging?
- I'll tell you when I've had enough.
- We've failed, that's all people will understand.
- Have you any idea what this tributary empties into?
- My boys used to tell me there's a lagoon at the end of it.
- Over hundreds of years, perhaps over thousands of years, the current would break it up.
- Even if David's theory is correct, the chances of finding anything are remote.
- Well, there's just one thing, going into unexplored territory with a woman.
[...]