Difference between Archimedes Law & Principle of Flotation
Archimedes’ Principle states that when a body is wholly or partially immersed in a fluid, it suffers an apparent loss of weight that is equal to the weight of fluid displaced.
Whereas
Principle of flotation: When a body is floating in a liquid, the weight of liquid displaced equals to the weight of the body.
Since the word fluid includes both, liquids and gases, and the fact that merchant ships are only expected to be partially immersed in water, the Principle of Flotation is a modified version of Archimedes’ Principle.
Ref: Ship Stability at Operational Level by Capt H Subramaniam