The Salish Sea refers to the combined waters of the Pacific Northwest. It is highly unlikely that any Salish native ever used the term in this sense, but there is enough interdependence of these waters and varied reasons to refer to them as a unit that the term has been adopted by the Geographic Boards of both the US and Canada. For our purposes at hand, we break this term up into Northern Waters, being the Strait of Juan de Fuca, the San Juan and Gulf Islands, and the Southern Straits of Georgia, leaving the Southern Part to be made up of Admiralty Inlet and Puget Sound. Note that though we do agree with Canada on the name of this grand combined waterway, we do not agree on the name of the Strait of Juan de Fuca, which they insist on calling the Juan de Fuca Strait!
And I should also add, that the reason we break up the waters this way is because the University of Washington Department of Atmospheric Sciences produces their highest resolution numerical weather predictions on these two separate map regions. Most local races are in one or the other of these parts, but there are a couple notable races that sail between them, and those will give the navigator a bit more work to do.