We have a "one point, one name" rule for bodies of seawater.  The name given to this point is "Strait of Georgia".  The way that I would prefer to apply a larger, more over-arching name, is to create some kind of "meta-relation" with that name, and have the individually named bodies of water within it as "subarea" roles.  So in this case, the Strait of Georgia would be a subarea within the Salish Sea, thus the name "Strait of Georgia" would be applied to the main relation for this point, and the name "Salish Sea" would have to be applied to a meta-relation with the Strait of Georgia as a member, with "subarea" role.