The correct answer is Archimedes' principle.
Concept:
Archimedes principle:
the principle of Archimedes states “When a body is immersed in a liquid, an upward thrust, equal to the weight of the liquid displaced, acts on it.”

Thus, when a solid is fully immersed in a liquid, it loses weight which is equal to the weight of the liquid it displaces.
i.e., \(Apperent\;weight = actual\;weight - buoyant\;force = mg - \rho gV\)
where m is mass of the object, ρ is the density of the fluid
Hence if there is no gravity, there is no Upward Thrust.
The upward force applied to the object is called the buoyant force.
Here,
ρ = density of liquid
g = acceleration due to gravity
V = volume of liquid displaced by the object
Explanation:
Archimedes’ principle, a physical law of buoyancy states that any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force the magnitude of which is equal to the weight of the fluid displaced by the body.
Hence floating of the ship is based on Archimedes principle: