Two solid spheres of identical physical volume—one made of solid lead and the other made of solid aluminum—are both completely submerged under water. How do the buoyant forces acting on them compare?

The buoyant forces are exactly identical.

Explanation

According to Archimedes' principle, the buoyant force depends solely on the volume of the displaced fluid. Since both spheres are completely submerged and have identical physical volumes, they displace the exact same weight of water and experience identical upward buoyant forces.