Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object -- Archimedes of Syracuse.

Archimedes' Principle formula:
  F = V * g * (ρ_f - ρ₀)

where:
  V: Volumen of the Object, in m³
  F: Buoyant force of the object, in Newton
  g: acceleration due to gravity, is 9.80665m/s^2
  ρ_f: Density of the object
  ρ₀: Density of the fluid