Translation
It is the still pool that is home to crocodiles.
Application
Quiet individuals who appear mild and timid often do bold and unbelievable things, especially when viewed through the lens of how others perceive them.
OR
Never underestimate the capabilities of your adversary; even those who appear weak or unthreatening can prove to be more powerful or capable than expected.
Similar Proverbs
1. Chidziva mudingwi ndicho chinogara ngwena.