Still Waters Run Deep

The expression "still waters run deep" is generally used to say that someone who appears simple may in fact be very complex internally. As a metaphor it means a seemingly uninteresting thing, still waters, has a whole lot hidden beneath it's surface. Personally, I don't think thats very true. Honestly, there are people who are "deep" and those who are superficial no matter how they act. I don't think it pertains to any one group. To me its kind of a generalization. The opposite of this statement, all outgoing people are shallow would not go over well. However being deep is recognized as a good thing so I doubt many people would have a problem with it.