It's possible that this phrase is a variation of another idiom or a new expression being used to convey a particular meaning. However, without more context, it's difficult to determine its intended message.
Here are some possible interpretations:
* Literal meaning: The saying could literally mean that the best fish are found in deeper waters, perhaps because of better food sources or less competition.
* Figurative meaning: It could be a metaphor for valuable things being hidden or overlooked, like the best people are often unassuming and humble.
* Contextual meaning: Depending on the context, the phrase might be intended to convey a different meaning entirely.
If you can provide more information about where you encountered this phrase, it might be easier to decipher its meaning.