When a ship enters from an ocean to a river, it will experience a decrease in buoyancy due to the decrease in water density.
River water is typically less dense than seawater because it has a lower salinity.
As a result, the ship will sink slightly more into the water, but it will not completely sink.
This is because the ship's weight is still balanced by the buoyant force exerted by the surrounding water.
However, the ship may experience some changes in its stability and draft due to the change in water density, and it may need to adjust its ballast or cargo to maintain its stability.