What does brackish mean?

Brackish is the mix of salt and fresh waters often found in lakes, bays and other estuaries (Chesapeake Bay being the largest in USA) all over the world. The salinity is between .5 - .30 ppt (parts per thousand) and salinities can vary due to rainfall and other seasonal factors. Slightly salty or as we like to describe it as, "A little salty. A little fresh."