Why does the buoyancy of a ship from the sea to the river remain unchanged, while that of a submarine from the sea to the river decreases? Why does the buoyancy of a ship remain unchanged?

Why does the buoyancy of a ship from the sea to the river remain unchanged, while that of a submarine from the sea to the river decreases? Why does the buoyancy of a ship remain unchanged?

1. Ship: first of all, no matter where the ship is, its mass and gravity change. According to the balance of the two forces, its buoyancy also changes (so the V row of the ship changes)
2. Submarine: the principle of a submarine is to sink and float by increasing its drainage and water absorption and reducing its own gravity. In addition, when the submarine is completely submerged in the water, the V row does not change, but the ρ in the water becomes smaller, so the buoyancy becomes smaller (at this time, the submarine will sink. At this time, in order to maintain the previous state, the submarine will drain to reduce its own gravity and achieve balance)