"Still waters run deep."
Some rivers have rough surfaces with waves. That's usually
because the water is shallow and there are rocks near the
surface. But deep rivers have no rocks near the surface and
the water is smooth and still. This proverb means that
people who are calm and quiet on the outside, often have
a strong, "deep" personality inside.
Hope that helps. Why don't you post your writing here, perhaps others can give more advice.