Caissons floating after the dry dock has been flooded, 1965

The flooding of the dry dock took eight days. The perfectly sealed caissons floated to the surface despite their 32,000-ton weight. This is due to a phenomenon known as Archimedes’ principle, which states that if an object containing an amount of air equal to its own weight is immersed in a fluid at rest, it will be buoyed up by a force equal to the weight of the fluid displaced.