Puget Sound - ebb vs. flood currents

A perplexing and interesting thing I have noticed about the surface currents as predicted by NOAA is that the ebbs are ALWAYS much faster than the floods.  Since basically the same amount of water is moving in and out it seems to me this indicates the flood comes in from the bottom and the ebb goes out on the top.

Any scuba divers have an insight?

http://en.wikipedia.org/wiki/Estuarine_water_circulation

Salt water does encroach from the bottom and lighter freshwater tends to float on top.   In  a system with freshwater input, ebbs are going to be faster then floods.

Awesome.  Thanks.