Floating ships made out of iron...

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Because of its greater volume, the ship displaces more water in comparison to the steel block.

Due to Archimedes' principle, in water a force exerts in the opposite direction to the gravitational force of the ship. This force is called buoyant force.

As floating, the gravitational force of the floating body equals its buoyancy. Because they exert in the opposite direction, the resultant equals zero.
Therefore, the ship sinks into the water until the buoyant force equals the gravitational force of the ship.

Which magnitudes change if the ship is loaded up?