  The acceleration of a light buoyant object in a fluid is analyzed.
Misconceptions about the magnitude of that acceleration are briefly described
and refuted. The notion of the added mass is explained and the added mass is
computed for an ellipsoid of revolution. A simple approximation scheme is
employed to derive the added mass of a slender body. The slender-body limit is
non-analytic, indicating a singular character of the perturbation due to the
thickness of the body. An experimental determination of the acceleration is
presented and found to agree well with the theoretical prediction. The added
mass illustrates the concept of mass renormalization in an accessible manner.

Fluid Dynamics;High Energy Physics - Phenomenology;High Energy Physics - Theory