A ship sailing through the St. Lawrence River (fresh water) enters the Atlantic Ocean (salt water). At equilibrium the ship will sit {higher or lower} in the Atlantic Ocean (salt water) compared to the St. Lawrence River (fresh water).
Look up the density of saltwater and the density of fresh water. The ship will sit higher in the liquid with greater density.
The density of the water displaced times the volume of the water displaced is equal to the weight of the ship. A fluid with a greater density will require less volume of liquid to be displaced, so the object will sit higher in that fluid