Finds the buoyant force as the density of the fluid × the volume displaced × gravity. The upward force is exactly the weight of the fluid pushed aside.
Anything immersed in a fluid feels an upward push, and its size is exactly the weight of the fluid it displaces. That is Archimedes' principle.
Here is the density of the fluid, the volume displaced and gravity.
What the object is made of does not enter into it. Iron or wood, the same submerged volume gets the same push.
Fully submerge an object of 1000 cm³, that is one litre, in water of density 1 g/cm³.
It displaces 1000 g, one kilogram, of water, so the buoyant force is
Underwater the object feels a kilogram lighter than it does in air.
It comes down to comparing two densities.
Ice has a density of 0.917 g/cm³, just under water's, so it floats — but only just. 91.7% of it stays below the surface, leaving 8.3% in the air. The phrase "tip of the iceberg" is a precise statement of physics.
Steel is 7.9 g/cm³, eight times denser than water. Ships float anyway because a ship is not a solid lump of steel.
The hull encloses air. The average density of the whole vessel, steel and air together, is deliberately kept below that of water, so the displaced water outweighs the ship. Load more cargo and the average density rises, and the ship settles deeper.