ஆற்றில் ஒரு மீன் பாய்ந்தால் ஆழம் தெரியுமா?
Aatril oru meen paayndhaal aazham theriyumaa?
Meaning
Watching one fish leap in a river tells you nothing about how deep it is - a single instance is no basis for judging the whole truth.
Story
A traveller saw a small fish leap near the bank and decided, "this river can't be very deep," and waded straight in. A few steps later the water was over his head. He learned that day that one fish's leap tells you nothing about a river's true depth.
Reader's Note
Gather enough information before deciding - snap judgments can be dangerous.