buoyancy

And if your buoyancy force happens to be less than the force from gravity, you sink.

If you remember your lessons on buoyancy, you know that a ship displaces its own weight in water.

The turbulence of the hydraulic jump entrains a lot of air, reducing the buoyancy of a swimmer.

Even the moon joined in on the operation, raising the tide in the canal to give a little more buoyancy to the foundered ship.